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Individuals often interact with others in their environment, whether it is multicellular organisms such as lions in a plain, or bacteria in a wound in a more microscopic level. These interactions are characterized by both the effect on the recipient of an action and the effect of the behavior on the initiator of the action. For many years altruistic interactions, those that benefit the recipient but impose a cost on the actor, confounded evolutionary biologists because they seem to provide a perfect setting for cheating, where individuals could gain the benefits of cooperative individuals without contributing to the public good (Hamilton, 1964a; Hamilton, 1964b; Axelrod & Hamilton, 1981; Lehmann & Keller, 2006; Ghoul, Griffin & West, 2014). In this setting, a cooperative population would be overcome with cheaters, leading to its collapse. However, Hamilton (1964a) showed that altruism could evolve if individuals preferentially directed benefits to kin. This theory, known as kin selection, requires individuals to be sufficiently related to overcome the costs of their cooperative behaviors.

At its face, kin selection, while a social behavior, is a solitary interaction between two individuals. Individual A senses individual B and based on some cue, be it genetic or environmental, either directs resources towards B or not (Hurst & Beynon, 2010; Coffin, Watters & Mateo, 2011; Leclaire et al., 2013). Yet there are many social behaviors that require the collective action of a group of individuals. In higher organisms, the flight patterns of migratory birds, group babysitting in meerkats, and schooling in fish are all examples of collective action. Just as in other social behaviors, they are mirrored in microbes. For example, there is swarming in Myxoccocus xanthus and fruiting body formation in Dictyostelium (Crespi, 2001; Velicer & Yu, 2003). In microbes, many studies have shown that relatedness is necessary for collective actions (Ross-Gillespie & Kümmerli, 2014). By studying both kin selection and collective behaviors in both higher organisms and microbes, we can gain a deeper understanding of the evolution of multicellularity, a collective action where independent individuals give up their own autonomy to form a higher-level group (Szathmáry & Smith, 1995; Queller, 2000).

Dictyostelium discoideum can be used for the study of both individual (kin recognition) and collective actions (development) making it ideal for the study of multicellularity. D. discoideum reproduces by binary fission and preys on soil bacteria. When resources become scarce, individuals send out a chemical signal that causes all nearby cells to aggregate together and initiate development. Once aggregated, the cells begin differentiating. The majority of the cells, approximately 80% will form reproductive spores while the remaining cells will altruistically form sterile stalk (Kessin, 2001). Unlike metazoans that go through a single-cell bottleneck at the zygote stage, Dictyostelium forms a metazoan-like aggregate that may be made up of several genotypes, thus providing an arena for competition, conflict, and manipulation.

Indeed, cheaters have been identified that are consistently over-represented in the sorus when mixed with another strain in both nature and in the laboratory setting (Strassmann, Zhu & Queller, 2000; Fortunato, Queller & Strassmann, 2003; Queller et al., 2003; Gilbert et al., 2007). However, all of these experiments were done bypassing a part of the lifecycle that involves another collective action—migration. If the present environment is not conducive to reproductive success, the group of cells, now known as a slug, can collectively migrate to a better location to finish development (Kessin, 2001). While it seems like there should not be any conflict within the slug, because this process allows cells to escape a poor environment, there is evidence of some conflict. Foster et al. (2002) found that clonal slugs travel further than chimeric slugs composed of the same number of cells. This conflict could be avoided if the cells segregated to form separate slugs but experiments show that larger slugs move faster than smaller slugs and that a larger chimeric slug will travel further than smaller clonal ones, which could make a huge difference if a slug is attempting to reach a favorable location (Inouye & Takeuchi, 1980; Foster et al., 2002).

We know that there is competition between genotypes when there is no slug migration but why during the migration stage? The cells risk death if they aggregate in a location that is not conducive to dispersal and reproduction so why isn’t there some type of armistice while migrating? It turns out that slug migration is costly (Jack et al., 2011). As the slug moves, prestalk cells are left behind in a slime trail (Bonner, Koontz & Paton , 1953; Sternfeld, 1992; Kuzdzal-Fick et al., 2007). The remaining cells must redifferentiate to maintain the proper slug proportioning of prestalk and prespore cells, which leads to a decrease in the number of reproductive spores that are formed (Abe et al., 1994; Ràfols et al., 2001; Jack et al., 2011). Decreasing the number of reproductive spores may set the stage for increased conflict if the slug is not homogeneous, similar to how limited resources may cause escalation of fights between higher organisms. For this reason, we predict that prolonging the time heterogeneous slugs migrate will accentuate competition because it prolongs the time genotypes compete against each other and decreases the availability of reproductive spores.

Materials & Methods

Growth and maintenance of strains

We used five naturally occurring clones of D. discoideum (NC28.1, NC34.1, NC63.2, NC85.2 and NC105.1) originally collected in North Carolina (Francis & Eisenberg, 1993), which have been used in several previous studies on the social behavior of D. discoideum (e.g., Fortunato, Queller & Strassmann, 2003; Buttery et al., 2009). We grew spores from frozen stocks on SM agar plates (10 g peptone, 1 g yeast extract, 10 g glucose, 1.9 g KH2PO4, 1.3 g K2HPO4, 0.49 g MgSO4 (anhydrous) and 17 g of agar per liter) in the presence of Klebsiella aerogenes (Ka) bacteria at a temperature of 22 °C.

Transformation of wild clones

We collected actively growing and dividing cells from the edges of plaques grown in association with Ka on SM agar plates and transferred them to HL5 axenic medium (5 g proteose peptone, 5 g thiotone E peptone, 10 g glucose, 5 g yeast extract, 0.35 g Na2HPO4 ⋅ 7H2O, 0.35 g KH2PO4 per liter (Watts & Ashworth, 1970)) + 1% PVS (100,000 units of penicillin, 100 mg streptomycin sulphate, 200 µg folate, 600 µg vitamin B12 per liter) that was changed daily. The HL5 was changed daily until the culture dishes were free of visible bacteria. We then harvested the cells and washed them twice by centrifugation and resuspended them in cold standard KK2 buffer (16.1 mM KH2PO4 and 3.7 mM K2HPO4). Once the culture dishes were free of visible bacteria, we followed the procedure for the transformation of D. discoideum by (Pang, Lynes & Knecht, 1999) with red fluorescent protein (RFP) on an actin-15 promoter and a G418-resistance cassette.

The cells were transferred to culture dishes containing HL5 + 1% PVS and left overnight. After 24 h the medium was replaced with fresh medium containing 20 µg/ml G418 and changed daily for five days of selection. Wild D. discoideum clones do not grow well in axenic medium so we transferred the amoebae to SM agar with Ka to propagate. Plaques that fluoresced red under a (535 nm) light source were transferred to G418-SM agar plates (30 µg/ml G418) in the presence of G418 resistant Ka for a final round of selection. Stable clones were then mixed in equal proportions with their ancestor and allowed to develop. Those that did not significantly differ in proportion when mixed with their ancestor and allowed to develop were used in the assay (see Figs. S1 and S2).

Cell preparation and migration assay

We washed harvested log-phase cells free of bacteria by repeated centrifugation and suspended them in KK2 buffer at a density of 1 × 108 cells/ml. We made 50:50 chimeric mixes of each RFP clone against all other ancestor clones, with a total of 10 chimeric mixes.

We placed 1.5% water agar Petri plates (size: 150 × 15 mm) in a laminar flow hood to remove excess moisture. We then drew a line on the underside of the plates that was 2 cm from the edge of the plate so that a line of 1 × 107 cells could be applied with accuracy and dried beneath a laminar flow hood for an additional 45 min. For each treatment there were 20 plates: ten chimeric mixes and ten clonal mixes (all 5 ancestors and their RFP-transformants).

We set up two different treatments: non-migration and migration. For the non-migration treatment, plates of each clone or mix were wrapped individually in foil with a 0.5 cm wide slit cut over the cells and then placed in an incubator where they could receive light from above, a condition which causes them to fruit without first migrating. For the migration treatment, plates were aligned and stacked with paper circles between each one. The plates were then wrapped in aluminum foil, leaving a small opening at the end of the plates opposite to the cells. This provided a directional light gradient for the aggregates to phototactically move toward. The plates from both treatments were incubated for 6 days in 24-hour light, before being unwrapped and placed beneath a unidirectional light source to induce fruiting of any slugs that remained. Each pair of treatments was replicated five times.

To measure migration distance, we followed the procedure in Jack et al. (2011) where the plate was marked in 2 cm wide zones parallel to the original line they were applied and counted the number of fruiting bodies per zone using a dissecting microscope.

Estimation of spore allocation and rate of spore loss

Spore production

Spore allocation was measured using spore production as a proxy. The fruiting bodies were carefully scraped up with a modified spatula and added to 3 mL of spore buffer (20 mM EDTA and 0.1% NP-40). To calculate spore production, the total number of spores was estimated and divided by the original number of cells.

To estimate the proportions of spores of both strains in a chimeric fruiting body, we counted the proportion of RFP-labeled cells using a fluorescent microscope, correcting for loss of labeling from the clonally plated RFP genotypes. To reduce sampling error, we counted at least 250 spores.

Rate of spore loss

We calculated the rate of spore lost as the decrease in spore production per centimeter traveled. We took the difference in spore production between the No Migration and Migration treatments and divided by the difference in distance traveled between the Migration and No Migration treatments. Standardizing for distance traveled allows us to accurately compare the proportion of spores that were lost for both treatments.

Measuring cheating and facultative behavior

We calculated the spore production for each pair both clonally and chimerically following the procedure in (Buttery et al., 2009). Clonal spore production varies between genotypes. This is equivalent to fixed allocation cheating and must be accounted for when measuring facultative behavior. Facultative behavior is measured as the deviation from clonal spore production when in chimera. The amount of facultative behavior was calculated as the sum of the degree to which a genotype’s own spore production increased (‘self-promotion’) and the amount it could reduce its competitors’ (‘coercion’) during social competition. The values for coercion and self-promotion can be plotted as coordinates on a grid (Fig. 4). The origin stands for no change in behavior. Any deviation from the origin is considered facultative behavior. We compared the lengths of the vectors for the migration and no migration treatments.

We measured spore-stalk ratio directly from fruiting body architecture by estimating volumes. We calculated stalk volume using the average width of the stalk measured across the bottom, middle, and top of the stalk and the stalk length. We calculated spore allocation as the volume of the sorus divided by the volume of the whole fruiting body (Buttery et al., 2009). Seven or eight fruiting bodies from each clone or chimeric pair were measured.

Statistical analysis

All statistical analyses were calculated using R software version 3.0 (www.r-project.org). Because of the ‘round robin’ nature of the experimental design, data were analyzed as nested ANOVAs, using 1-way or 2-way ANOVAs depending upon the number of factors in the analysis. This allowed us to control for variation between replicates.

Chimerism and migration

On average, slugs in the migration treatment traveled 5.76 ± 0.017 cm while slugs from the no migration treatment traveled 0.093 ± 0.002 cm (1-way nested ANOVA: F6,214 = 476.02, P < 0.001). We found that clonal genotypes vary in the distance they migrate (Fig. 1; 1-way nested ANOVA: F4,34 = 7.55; P < 0.001). Chimeric slugs migrated less far than would have been expected from the average of the migration distance of the two constituent clones (Fig. 2A; observed mean = 5.50 ± 0.24 cm, expected mean = 6.19 ± 0.20 cm; 1-way nested ANOVA: F1,49 = 17.86, P < 0.001). When we calculated the decrease in spore production per centimeter traveled, we did not find a significant difference between clonal slugs (µ = − 0.040 ± 0.004 spores per cell/cm) and chimeric slugs (µ = − 0.046 ± 0.005 spores per cell/cm; Fig. 2B—one-way ANOVA; F1,93 = 0.83, p = 0.365).

Migration distance is genotype specific.

Figure 1: Migration distance is genotype specific.

An equal number of cells of each clone was placed on water agar plates to form slugs. The slugs migrated under a unidirectional light source for six days and were then allowed to fruit. An average migration distance per plate was calculated. The Tukey boxplots shows the distribution of ten replicates (five untransformed, five RFP transformed) for each clone. (1-way nested ANOVA: F4,34 = 7.55, P < 0.001).
Chimeric slugs travel less far than clonal slugs but lose cells over distance at a similar rate.

Figure 2: Chimeric slugs travel less far than clonal slugs but lose cells over distance at a similar rate.

(A) Using the clonal migration distances from Fig. 1, we calculated the expected migration distances for chimeric slugs that developed from the same total number of cells. The Tukey boxplots show that migration distance for chimeric slugs were lower compared to clonal slugs (observed mean = 5.50 ± 0.24 cm, expected mean = 6.19 ± 0.20; 1-way nested ANOVA: F1,49 = 17.89, P < 0.001). (B) However, the decreased migration did not seem to affect spore production as there was not a significant difference in the number of spores lost per cm traveled between clonal and chimeric fruiting bodies after migrating (1-way nested ANOVA: F1,93 = 0.83, P = 0.365).

Migration affects spore production and allocation

We found that chimeric fruiting bodies contain more spores than clonal fruiting bodies, though the difference was only marginally significant. This confirms a previous significant result (Buttery et al., 2009). Chimeric fruiting bodies produced more spores compared to clonal fruiting bodies both with and without migration. The fruiting bodies of aggregates that migrated produced significantly fewer spores than those that did not migrate (Fig. 3A; 2-way nested ANOVA: clonal vs. chimeric: F1,73 = 2.76, P = 0.066, μCL = 0.214 ± 0.011 spores per cell, μCH = 0.247 ± 0.017 spores per cell; migration vs. non-migration: F1,73 = 133.9, P < 0.001, μM = 0.117 ± 0.006 spores per cell, μNM = 0.345 ± 0.015 spores per cell).

Spore production and fruiting body architecture is affected by migration and whether fruiting bodies are clonal or chimeric.

Figure 3: Spore production and fruiting body architecture is affected by migration and whether fruiting bodies are clonal or chimeric.

The Tukey boxplots compare different measurements of fruiting body production between groups and treatments. (A) This shows that clones that migrated had a significantly lower spore production than fruiting bodies that did not, indicating the loss of cells as the slugs migrated. Chimeric fruiting bodies had a higher, marginally significant, spore production compared to clonal fruiting bodies across both non-migration and migration treatments (2-way nested ANOVA: non-migration vs. migration: F1,73 = 133.9, P < 0.001; clonal vs. chimeric: F1,73 = 2.76, P = 0.063). (B) The ratio of sorus volume to total fruiting body volume of migrated fruiting bodies are significantly higher compared to those of the non-migration treatment, irrespective of whether the fruiting bodies were clonal or chimeric (1-way nested ANOVA: F1,24 = 10.46, P = 0.004). (C) The higher ratio of sorus to fruiting body shown in B may be explained because fruiting bodies that have migrated have significantly shorter stalks than those that did not migrate (1-way nested ANOVA: F1,60 = 804.1, P < 0.0001).
Facultative cheating behavior is reduced after migration.

Figure 4: Facultative cheating behavior is reduced after migration.

Facultative cheating, the deviation from clonal spore production when in chimera is the sum of ‘self-promotion’ and ‘coercion,’ is shown in the Tukey boxplots as their overall behavior. Overall, this cheating behavior decreased by approximately 50% for fruiting bodies that migrated compared to those that did not (1-way nested ANOVA: F1,22 = 22.18, P < 0.001).

We found significant differences in fruiting body architecture between aggregates that migrated and those that did not. From the morphometric analysis of fruiting body structure, we found that fruiting bodies that migrated allocated proportionately more to spores than those that did not (Fig. 3B; 1-way nested ANOVA: F1,24 = 10.46, P = 0.004, μM = 0.933 ± 0.01, μNM = 0.836 ± 0.014). This was true for both clonal and chimeric aggregates. As expected from this result, aggregates that migrated had shorter stalks than those that did not (Fig. 3C; 1-way nested ANOVA: F1,60 = 804.1, P < 0.0001, μM = 311.24 ± 11.71 mm, μNM = 1046.47 ± 27.23 mm).

Migration causes a decrease in cheating behavior

We estimated the amount of fixed cheating and facultative cheating between the two treatments by comparing the spore production of clonal and chimeric fruiting bodies. We found no differences in relative fixed allocations (i.e., clonal spore allocation) when we compared spore allocation with and without migration. However, there was significantly less facultative cheating behavior within chimeras that migrated compared to those that did not (Fig. 4; 1-way ANOVA: F1,22 = 22.18, P < 0.001, μM = 0.086 ± 0.014, μNM = 0.175 ± 0.02).

Previous studies have found cheating in D. discoideum and that it can be divided into two categories: fixed and facultative (Strassmann, Zhu & Queller, 2000; Fortunato, Queller & Strassmann, 2003; Queller et al., 2003; Gilbert et al., 2007; Buttery et al., 2009). The proportion of cells allocated to spore vs. stalk is generally a genotype-specific trait, so if a high spore allocator is mixed with a low spore allocator, the high spore allocator is expected to be overrepresented in the sorus. This is fixed cheating, and the degree to which it occurs can be predicted from genotypes’ clonal behavior (Buttery et al., 2009). Facultative cheating occurs when there is a significant deviation from the behavior exhibited under clonal conditions. Genotypes that cheat by increasing their own allocation to spores are ‘self-promoters’ and those that can reduce their partner’s share are ‘coercers’ (Buttery et al., 2009; Parkinson et al., 2011). Partitioning cheating behaviors have given us a lot of new insight in kin conflict in D. discoideum, but these studies are limited because they do not focus on competition during the migration stage, which makes up a large portion of the social life cycle.

In this study, we examined the interplay of two seemingly diametric actions, the solitary action of kin recognition and the collective action of slug migration in D. discoideum, to more fully understand the effects of social competition on fitness over the entire lifecycle. The study by Foster et al. (2002) found that chimeric slugs did not travel as far as clonal slugs of the same size. They hypothesized that internal conflict was preventing the slugs from traveling greater distances. The anatomy of the Dictyostelium slug is such that the front of the slug is where the cells that will eventually become stalk are located. They suggested that the unwillingness to be in the front of the slug might be the cause of the shorter distances. More recent studies suggest that response to DIF-1, a polyketide produced by prespore cells that induce differentiation into stalk, can predict whether a clone is likely to cheat or be a cheater (Parkinson et al., 2011). Clones that were more sensitive to DIF-1 were more likely to end up in the stalk. Our initial hypothesis was that if social competition is prolonged by migration towards light, the behavior of cheaters would be exaggerated if cheating is an active process where clones can either change their behavior if they sense a competitor or change the behavior of their competitor. We predicted that the lower relatedness of the chimeric slugs would increase the conflict within the slug, thus decreasing the probability of cells working as a cohesive unit to migrate and increasing the fitness of cheater clones.

Overall, our hypothesis was not supported. Although we did find a cost in distance traveled when we compared chimeric and clonal slugs, the difference was not nearly as large as that as in the study by Foster et al. (2002). Castillo et al. (2005) showed that slugs found within shallow soil (1 cm from the surface) could easily travel to the surface, whether or not they were chimeric and that neither clonal nor chimeric slugs could easily reach the surface when under a 5 cm-deep layer of soil. Additionally, cells sloughed during migration will have seeded new colonies should the slug pass through a patch of bacterial food (Kuzdzal-Fick et al., 2007), so even if the slug is unable to make it completely through to the soil surface, the cells from the slug will still have the opportunity to replicate. Most interestingly, instead of finding increased cheating, the outcome of our interactions showed a decrease in cheating behavior when chimeric slugs were allowed to migrate compared to when they were not. Weaker clones from the no migration treatment had increased spore representation in the migration treatment suggesting that migration reduced the costs associated with being a chimeric slug. There are two possible explanations for our results. A recent paper found that kin recognition is lost during the slug stage and that kin discrimination and cheating both decrease as development proceeds (Ho & Shaulsky, 2015). Slug migration lengthens the development time, as D. discoideum does not begin differentiating until it has reached a new location. It is possible that the decrease in facultative cheating is related to the tgrB1 and tgrC1 genes decreased expression levels, which leads to less kin recognition. Another possible explanation is related to the production of DIF-1. Those clones that migrated the farthest (Fig. 1) were also the clones that were most likely to be facultative cheaters according to (Parkinson et al., 2011). These clones are the ones that show the least response to DIF-1 and produced the most. If in chimeras, these longer migrating clones are no longer at the front, it could explain why chimeric slugs travel shorter distances than clonal slugs. Additionally, it is possible that the act of migration is energetically costly, so that these clones produce less DIF-1. If that were the case, then clones that are more sensitive to it under non-migration circumstances would show increased spore production, which would give the results that we saw—more equitable distribution of spores.

When we compared our morphometric analysis of fruiting bodies for all treatments, we found another consequence of migration. We found that spore-stalk allocation increases with migration for both clonal and chimeric treatments. This may be a non-adaptive response to the decreased DIF-1 production. Or, producing proportionally less stalk after prolonged migration may be a useful strategy; stalk height may be less important if the slug has migrated into a more suitable habitat for dispersal. Dictyostelid spores are sticky, and therefore not likely to be dispersed by wind, but viable spores from dictyostelids have been found in the digestive contents of earthworms, nematodes, and other soil invertebrates, which can act as mid-distance dispersers or can travel over even longer distances in the digestive tracts of birds and mammals (Suthers, 1985; Huss, 1989; Sathe et al., 2010).

Collective cell and animal behavior is useful for understanding the evolution of multicellularity. Migration in D. discoideum encompasses concepts from both types of behavior. Collective cell migration is necessary for two of the key processes of embryonic development: gastrulation and organogenesis (Weijer, 2009). Cell migration in Dictyostelium is very similar (Weijer, 2009). Both involve cells that are close together, migrate easily, move collectively in response to a signal, use actin and cell–cell junctions to provide traction, and have an extracellular matrix (Friedl & Gilmour, 2009; Weijer, 2009). Collective animal behaviors such as grouping and swarming involve self-organization and are found in both lower and higher organisms (Sumpter, 2006; Olson et al., 2013). They provide many benefits such as reducing the risk of predation, increase foraging efficiency, and improving mating success (Olson et al., 2013). For Dictyostelium, collective migration allows the cells to move more efficiently and for longer distances than individuals, much like the V formation in migrating geese. However, there are instances where individuals within a group may go rogue and only think of their own self-interest, such as when cheaters gain more of a public good than they contribute. Slug migration is beneficial to all cells because it aligns the interests of the cells towards migration. Our study suggests that migration may also lead to alleviation of the conflict of interests in heterogeneous slugs, which leads to a decrease in facultative cheating.

Supplemental Information

Pre-experiment clone RFP-fluorescent stability

DOI: 10.7717/peerj.1352/supp-1

Raw data from experiments

The tabs labeled sporeMig are the raw datasets collected from the migration plates. There are two tabs, one for chimeric data and one for clonal data. The tabs labeled with Morph are the morphometric datasets for the clonal and chimeric fruiting bodies.

DOI: 10.7717/peerj.1352/supp-2


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The Pentateuch (Greek for “five books”) designates the first five books of the Jewish and Christian Bible (Genesis, Exodus, Leviticus, Numbers, and Deuteronomy). Jewish tradition calls the five books Torah (Teaching, Law) because of the centrality of the Sinai covenant and legislation mediated through Moses.
The unity of the Pentateuch comes from the single story it tells. God creates the world and destines human beings for the blessings of progeny and land possession (Gn 1–3). As the human race expands, its evil conduct provokes God to send the flood to wipe out all but righteous Noah’s family. After the flood, the world is repopulated from his three sons, Ham, Shem, and Japheth (Gn 4–9). From them are descended the seventy nations of the civilized world whose offense this time (building a city rather than taking their assigned lands, Gn 10–11) provokes God to elect one family from the rest. Abraham and his wife, Sarah, landless and childless, are promised a child and the land of Canaan. Amid trials and fresh promises, a son (Isaac) is born to them and Abraham takes title to a sliver of Canaanite land, a kind of down payment for later possession (Gn 12–25). Gn 25–36 tells how their descendant Jacob becomes the father of twelve sons (because of which he is called “Israel”), and Gn 37–50 tells how the rejected brother Joseph saves the family from famine and brings them to Egypt.
In Egypt, a pharaoh who knew not Joseph subjects “the seventy sons of Jacob” (“the Hebrews”) to hard labor, keeping them from their land and destroying their male progeny (Ex 1). Moses is commissioned to lead the people out of Egypt to their own land (Ex 2–6). In ten plagues, the Lord defeats Pharaoh. Free at last, the Hebrews leave Egypt and journey to Mount Sinai (Ex 7–18), where they enter into a covenant to be the people of the Lord and be shaped by the Ten Commandments and other laws (Ex 19–24). Though the people commit apostasy when Moses goes back to the mountain for the plans of the dwelling (tabernacle), Moses’ intercession prevents the abrogation of the covenant by God (Ex 32–34). A principle has been established, however: even the people’s apostasy need not end their relationship with God. The book ends with the cloud and the glory taking possession of the tent of meeting (Ex 36:34–38). “The sons of Israel” in Ex 1:1 are the actual sons of Jacob/Israel the patriarch, but at the end of the book they are the nation Israel, for all the elements of nationhood in antiquity have been granted: a god (and temple), a leader, a land, and an authoritative tradition.
Israel remains at the holy mountain for almost a year. The entire block of material from Ex 19:1 to Nm 10:11 is situated at Sinai. The rituals of Leviticus and Numbers are delivered to Moses at the holy mountain, showing that Israel’s worship was instituted by God and part of the very fabric of the people’s life. Priestly material in the Book of Exodus (chaps. 25–31, 35–40) describes the basic institutions of Israelite worship (the tabernacle, its furniture, and priestly vestments). Leviticus, aptly called in rabbinic tradition the Priests’ Manual, lays down the role of priests to teach Israel the distinction between clean and unclean and to see to their holiness. In Nm 10:11–22:1, the journey is resumed, this time from Sinai through the wilderness to Transjordan; Nm 22:2–36:13 tells of events and laws in the plains of Moab.
The final book of the Pentateuch, Deuteronomy, consists of four speeches by Moses to the people who have arrived at the plains of Moab, ready to conquer the land: 1:1–4:43; 4:44–28:68; 29:1–32:52; 33:1–34:12. Each speech is introduced by the formula “This is the law/words/blessing.”
The Priestly editor used literary formulas. The formula “These are the generations (the wording can vary) of... ” occurs five times in the primordial history (Gn 2:4a; 5:1; 6:9; 10:1; 11:10) and five times in the ancestral history (11:27; 25:12; 25:19; 36:1 [v. 9 is secondary]; 37:2). In Exodus and Numbers the formula (with slight variations) “They departed from (place name) and encamped at (place name)” occurs in two groups of six: A. Ex 12:37a; 13:20; 14:1–2; 15:22a; 16:1; 17:1a; and B. 19:2; Nm 10:12; 20:1a; 20:22; 21:10–11; 22:1.
Who wrote the Pentateuch, and when? Up to the seventeenth century, the virtually unanimous answer of Jews and Christians was “Moses.” Moses wrote the Pentateuch as David wrote the Psalter and Solomon wrote the wisdom literature. Though scholars had noted inconsistencies (compare Ishmael’s age in Gn 16:16 and 21:5, 14) and duplications (Gn 12, 20, and 26), they assumed Mosaic authorship because of the prevalent theory of inspiration: God inspired authors while they wrote. With the rise of historical criticism, scholars began to use the doublets and inconsistencies as clues to different authors and traditions.
By the late nineteenth century, one theory of the sources of the Pentateuch had been worked out that proved acceptable in its main lines to the majority of scholars (apart from Christian and Jewish conservatives) then and now. It can be quickly sketched. In the premonarchic period of the Judges (ca. 1220–1020 B.C.), the twelve tribes had an oral form of their story from creation to the taking of the land. With the beginnings of monarchy in the late eleventh and tenth centuries, the oral material was written down, being known as the Yahwist account (from its use of the divine name Yhwh). Its abbreviation, “J,” comes from the German spelling of the divine name. In the following century, another account took shape in the Northern Kingdom (called E after its use of Elohim as a divine name); some believe the E source is simply a supplement to J. After the fall of the Northern Kingdom in 722/721 B.C., the E version was taken to Jerusalem where it was combined with the J version to produce J-E. During the exile (conventionally dated 587–539 B.C.) or thereafter, an editor recast J-E to make it relevant for the exiled population. This editor is conventionally known as P (=Priestly) because of the chronological and ritual interests apparent in the work. P can also designate archival material and chronological notices. The audience for the Priestly edition no longer lived in the land and was deeply concerned about its survival and its claim on the land.
Deuteronomy (=D) stands alone in style, genre (preaching rather than narrative), and content. How did it come to be the fifth book of the Pentateuch? The J-E narrative actually ends in Numbers, when Israel arrives at the plains of Moab. Many scholars believe that Deuteronomy was secondarily attached to Numbers by moving the account of Moses’ death from its original place in the J-E version in Numbers to the end of Deuteronomy (chap. 34). Deuteronomy was attached to Genesis–Numbers to link it to another great work, the Deuteronomistic History (Joshua to Kings). Deuteronomy is now the fifth book of the Pentateuch and the first book of the Deuteronomistic History.
In the last three decades, the above consensus on the composition of the Pentateuch has come under attack. Some critics are extremely skeptical about the historical value of the so-called early traditions, and a few doubt there ever was a preexilic monarchy of any substance. For such scholars, the Pentateuch is a retrojection from the fourth or third centuries B.C. Other scholars postulate a different sequence of sources, or understand the sources differently.
How should a modern religiously minded person read the Pentateuch? First, readers have before them the most significant thing, the text of the Pentateuch. It is accurately preserved, reasonably well understood, and capable of touching audiences of every age. Take and read! Second, the controversies are about the sources of the Pentateuch, especially their antiquity and character. Many details will never be known, for the evidence is scanty. Indeed, the origin of many great literary works is obscure.
The Pentateuch witnesses to a coherent story that begins with the creation of the world and ends with Israel taking its land. The same story is in the historical Ps 44, 77, 78, 80, 105, 114, and 149, and in the confessions Dt 26:5–9, Jos 24:2–13, and 1 Sm 12:7–13. Though the narrative enthralls and entertains, as all great literature does, it is well to remember that it is a theopolitical charter as well, meant to establish how and why descendants of the patriarchs are a uniquely holy people among the world’s nations.
The destruction of the Jerusalem Temple and deportation of Israelites in the sixth century B.C. seemed to invalidate the charter, for Israel no longer possessed its land in any real sense. The last chapter of the ancient narrative—Israel dwelling securely in its land—no longer held true. The story had to be reinterpreted, and the Priestly editor is often credited with doing so. A preface (Gn 1) was added, emphasizing God’s intent that human beings continue in existence through their progeny and possess their own land. Good news, surely, to a devastated people wondering whether they would survive and repossess their ancestral land. The ending of the old story was changed to depict Israel at the threshold of the promised land (the plains of Moab) rather than in it. Henceforth, Israel would be a people oriented toward the land rather than possessing it. The revised ending could not be more suitable for Jews and Christians alike. Both peoples can imagine themselves on the threshold of the promised land, listening to the word of God in order to be able to enter it in the future. For Christians particularly, the Pentateuch portrays the pilgrim people waiting for the full realization of the kingdom of God.
Genesis is the first book of the Pentateuch (Genesis, Exodus, Leviticus, Numbers, Deuteronomy), the first section of the Jewish and the Christian Scriptures. Its title in English, “Genesis,” comes from the Greek of Gn 2:4, literally, “the book of the generation (genesis) of the heavens and earth.” Its title in the Jewish Scriptures is the opening Hebrew word, Bereshit, “in the beginning.”
The book has two major sections—the creation and expansion of the human race (2:4–11:9), and the story of Abraham and his descendants (11:10–50:26). The first section deals with God and the nations, and the second deals with God and a particular nation, Israel. The opening creation account (1:1–2:3) lifts up two themes that play major roles in each section—the divine command to the first couple (standing for the whole race) to produce offspring and to possess land (1:28). In the first section, progeny and land appear in the form of births and genealogies (chaps. 2–9) and allotment of land (chaps. 10–11), and in the second, progeny and land appear in the form of promises of descendants and land to the ancestors. Another indication of editing is the formulaic introduction, “this is the story; these are the descendants” (Hebrew tōledôt), which occurs five times in Section I (2:4; 5:1; 6:9; 10:1; 10:31) and five times in Section II (11:10; 25:12, 19; 36:1 [v. 9 is an addition]; 37:2).
The Composition of the Book. For the literary sources of Genesis, see Introduction to the Pentateuch. As far as the sources of Genesis are concerned, contemporary readers can reasonably assume that ancient traditions (J and E) were edited in the sixth or fifth century B.C. for a Jewish audience that had suffered the effects of the exile and was now largely living outside of Palestine. The editor highlighted themes of vital concern to this audience: God intends that every nation have posterity and land; the ancestors of Israel are models for their descendants who also live in hope rather than in full possession of what has been promised; the ancient covenant with God is eternal, remaining valid even when the human party has been unfaithful. By highlighting such concerns, the editor addressed the worries of exiled Israel and indeed of contemporary Jews and Christians.
Genesis 1–11. The seven-day creation account in Gn 1:1–2:3 tells of a God whose mere word creates a beautiful universe in which human beings are an integral and important part. Though Gn 2:4–3:24 is often regarded as “the second creation story,” the text suggests that the whole of 2:4–11:9 tells one story. The plot of Gn 2–11 (creation, the flood, renewed creation) has been borrowed from creation-flood stories attested in Mesopotamian literature of the second and early first millennia. In the Mesopotamian creation-flood stories, the gods created the human race as slaves whose task it was to manage the universe for them—giving them food, clothing, and honor in temple ceremonies. In an unforeseen development, however, the human race grew so numerous and noisy that the gods could not sleep. Deeply angered, the gods decided to destroy the race by a universal flood. One man and his family, however, secretly warned of the flood by his patron god, built a boat and survived. Soon regretting their impetuous decision, the gods created a revised version of humankind. The new race was created mortal so they would never again grow numerous and bother the gods. The authors of Genesis adapted the creation-flood story in accord with their views of God and humanity. For example, they attributed the fault to human sin rather than to divine miscalculation (6:5–7) and had God reaffirm without change the original creation (9:1–7). In the biblical version God is just, powerful, and not needy.
How should modern readers interpret the creation-flood story in Gn 2–11? The stories are neither history nor myth. “Myth” is an unsuitable term, for it has several different meanings and connotes untruth in popular English. “History” is equally misleading, for it suggests that the events actually took place. The best term is creation-flood story. Ancient Near Eastern thinkers did not have our methods of exploring serious questions. Instead, they used narratives for issues that we would call philosophical and theological. They added and subtracted narrative details and varied the plot as they sought meaning in the ancient stories. Their stories reveal a privileged time, when divine decisions were made that determined the future of the human race. The origin of something was thought to explain its present meaning, e.g., how God acts with justice and generosity, why human beings are rebellious, the nature of sexual attraction and marriage, why there are many peoples and languages. Though the stories may initially strike us as primitive and naive, they are in fact told with skill, compression, and subtlety. They provide profound answers to perennial questions about God and human beings.
Genesis 11–50. One Jewish tradition suggests that God, having been rebuffed in the attempt to forge a relationship with the nations, decided to concentrate on one nation in the hope that it would eventually bring in all the nations. The migration of Abraham’s family (11:26–31) is part of the general movement of the human race to take possession of their lands (see 10:32–11:9). Abraham, however, must come into possession of his land in a manner different from the nations, for he will not immediately possess it nor will he have descendants in the manner of the nations, for he is old and his wife is childless (12:1–9). Abraham and Sarah have to live with their God in trust and obedience until at last Isaac is born to them and they manage to buy a sliver of the land (the burial cave at Machpelah, chap. 23). Abraham’s humanity and faith offer a wonderful example to the exilic generation.
The historicity of the ancestral stories has been much discussed. Scholars have traditionally dated them sometime in the first half of the second millennium, though a few regard them as late (sixth or fifth century B.C.) and purely fictional. There is unfortunately no direct extra-biblical evidence confirming (or disproving) the stories. The ancestral stories have affinities, however, to late second-millennium stories of childless ancestors, and their proper names fit linguistic patterns attested in the second millennium. Given the lack of decisive evidence, it is reasonable to accept the Bible’s own chronology that the patriarchs were the ancestors of Israel and that they lived well before the exodus that is generally dated in the thirteenth century.
Gn 25:19–35:43 are about Jacob and his twelve sons. The stories are united by a geographical frame: Jacob lives in Canaan until his theft of the right of the firstborn from his brother Esau forces him to flee to Paddan-Aram (alternately Aram-Naharaim). There his uncle Laban tricks him as he earlier tricked his brother. But Jacob is blessed with wealth and sons. He returns to Canaan to receive the final blessing, land, and on the way is reconciled with his brother Esau. As the sons have reached the number of twelve, the patriarch can be given the name Israel (32:28; 35:10). The blessings given to Abraham are reaffirmed to Isaac and to Jacob.
The last cycle of ancestor stories is about Jacob’s son Joseph (37:1–50:26, though in chaps. 48–49 the focus swings back to Jacob). The Joseph stories are sophisticated in theme, deftly plotted, and show keen interest in the psychology of the characters. Jacob’s favoring of Joseph, the son of his beloved wife Rachel, provokes his brothers to kill him. Joseph escapes death through the intercession of Reuben, the eldest, and of Judah, but is sold into slavery in Egypt. In the immediately following chap. 38, Judah undergoes experiences similar to Joseph’s. Joseph, endowed by God with wisdom, becomes second only to Pharaoh in Egypt. From that powerful position, he encounters his unsuspecting brothers who have come to Egypt because of the famine, and tests them to see if they have repented. Joseph learns that they have given up their hatred because of their love for Israel, their father. Judah, who seems to have inherited the mantle of the failed oldest brother Reuben, expresses the brothers’ new and profound appreciation of their father and Joseph (chap. 44). At the end of Genesis, the entire family of Jacob/Israel is in Egypt, which prepares for the events in the Book of Exodus.
Genesis in Later Biblical Books. The historical and prophetic books constantly refer to the covenant with the ancestors Abraham, Isaac, and Jacob. Hos 10 sees the traits of Jacob in the behavior of the Israel of his own day. Is 51:2 cites Abraham and Sarah as a model for his dispirited community, for though only a couple, they became a great nation. Jn 1, “In the beginning was the word,” alludes to Gn 1:1 (and Prv 8:22) to show that Jesus is creating a new world. St. Paul interprets Jesus as the New Adam in Rom 5:14 and 1 Cor 15:22, 24, whose obedience brings life just as the Old Adam’s disobedience brought death. In Rom 4, Paul cites Abraham as someone who was righteous in God’s eyes centuries before the Law was given at Sinai.
Outline of Genesis.
Preamble. The Creation of the World (1:1–2:3)
I. The Story of the Nations (2:4–11:26)
A. The Creation of the Man and the Woman, Their Offspring, and the Spread of Civilization (2:4–4:26)
B. The Pre-flood Generations (5:1–6:8)
C. The Flood and the Renewed Blessing (6:9–9:29)
D. The Populating of the World and the Prideful City (10:1–11:9)
E. The Genealogy from Shem to Terah (11:10–26)
II. The Story of the Ancestors of Israel (11:27–50:26)
A. The Story of Abraham and Sarah (11:27–25:18)
B. The Story of Isaac and Jacob (25:19–36:43)
C. The Story of Joseph (37:1–50:26)


A Chief Amtrak Attendant In For The Long Haul

`I`ve Been Threatened By Irate Passengers`

March 20, 1988|By Beatrice Michaels Shapiro.

Growing up in the railroad town of Boone, Ia., Rex DuBois often went out to the railyards with his father, a retired railroader of 40 years. So it would seem only natural that DuBois would become the fourth railroad generation in his family. But that was not his original plan.

While working on a degree in business science, DuBois took a summer job with Amtrak in Chicago. He had every intention of finishing school, but, as he told writer Beatrice Michaels Shapiro, ``the atmosphere gets in your blood, and you just don`t want to leave.``

DuBois, 26, came to work at Amtrak in 1980 and has held various positions with the company. For the last four years he has served as Chief of OBS (On-Board Service), a supervisory job ``over almost every aspect of the train, except conductor.`` He works regularly on the City of New Orleans, which runs on the old Illinois Central Railroad route. He and his wife, Margaret, live in Crystal Lake with their son, Blake, 2 1/2.

Most long-haul trains in the system have a chief of OBS to ensure quality service to the passengers. We do everything from crew assignments, proper stocking of the train`s food and equipment, such as cooking utensils, to linens on sleeping cars. We also do visual mechanical inspection of the equipment in the yards before departure, and prior to each trip we take notice of any special services required by a passenger-whether that request be for kosher meals, storage of medications, handicapped assistance, oxygen, etc.-and then brief our crew accordingly.

I work a three-day-on and three-day-off schedule. My actual working hours on the train are 36. My first year as a chief I traveled quite a bit; I used to work regularly on the Eagle, the train going to San Antonio. Also, for the first 2 1/2 years as chief I dealt with special movements-trains chartered for special events, like the 20th Century Club Railroad moves, the Tulip Festival up in Holland, Mich., and Oktoberfest in Missouri. This was in addition to my regular job. I was transferred to the City of New Orleans in my second year. But in an emergency, I could go anywhere on short notice. In fact, I made three trips to San Antonio just this past June.

One of the reasons we are assigned to specific trains is to familiarize ourselves with the route, so we can make scenic announcements to the passengers and point out places of interest-it`s part of our job to do that. Then too, in case of an emergency, we are familiar with where we can get help when needed. On the City of New Orleans, we pass such places as the death site of the famous engineer Casey Jones, at Vaughan, Miss. We go through Champaign and Carbondale, the homes of the University of Illinois and Southern Illinois. Then we go down to Memphis, the home of Beale Street and the blues. Coming into Memphis, you get a glimpse of the Mississippi, but contrary to what people think, we don`t cross the big river. We cross the Ohio at Cairo, Ill., and then come along the east side of the Mississippi. It`s usually midnight or 5 in the morning at that point, so we don`t announce it. Our schedule time is right at 18 hours.

What`s an average day? Most chiefs are on duty approximately 5:30 a.m. We check the dining car to make sure the crew is there and that proper preparations are ready for a breakfast seating at 6:30 a.m. I check that sanitation standards are followed: cooking procedures, storage of food. Then I take a casual walk through the train, checking for cleanliness of the restrooms, the lounge and making sure all the attendants are doing their job. As to the crew, the dining car is made up of numerous employees, of which a dining car attendant is in charge. He has waiters, working under him, who are resonsible for taking care of tables. In the kitchen a chef is responsible for cooking the meals, freshly prepared from a frozen entree, aboard most long-haul trains. A second or possibly a third cook is responsible for the plating and presentation of the food. The lounge attendant is responsible for his own stock-hot and cold sandwiches, beverages and an assortment of alcohol, which he sells directly to the public. The coach-car attendant and the assistant conductor help the passengers with their luggage to board the train. They seat the passengers and provide pillow service and literature. The sleeping-car attendant offers wakeup service, coffee service and makes up the beds and ensures the cleanliness of the car. All long-haul trains have dining, lounge and sleeping cars.

At times I`ve had to take over for one of the attendants who, for instance, got sick en route. It`s a rude awakening. Supervising a job is not the same as actually doing the job. It really requires a lot of organization, I respect the crew for the job they do.


Salvador, Bahia (Pelourinho)
Cachoeira, Bahia
Bezerros, Pernambuco
Juazeiro Do Norte, Ceara
Aurora, Ceara

Pamplona Alta, Lima

The city of Salvador was founded in 1549 on the Bay of All Saints on the northeast coast of Brazil. It was the first capital of Brazil and was for centuries a center of the African slave trade. Salvador is the third largest city in Brazil (after São Paulo and Rio de Janeiro). Its historic center is called the Pelourinho, which boasts the largest concentration of 17th–19th century colonial architecture in the Americas and which was named a UNESCO World Heritage site in 1985. The city’s rich African heritage colors its cultural life and popular art: its cuisine, music, art, and religious and civic celebrations. The Pelourinho is home to many popular artists whose colorful work can be found displayed in local galleries and even on the streets.

salvador map


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