john hawks weblog

paleoanthropology, genetics and evolution

diet

  • Orangutan loris capture and meat-eating

    Fri, 2012-01-20 16:38 -- John Hawks

    Madeleine Hardus and colleagues [1] describe long-term observations of hunting by Sumatran orangutans.

    The paper is straightforward in its description of the hunting observations: They hunt slow lorises, the practice is rare, it occurs at times when their other preferred foods are scarce, some individuals hunt but most don't, and food sharing among individuals other than mother-infant pairs wasn't observed. This isn't the first time hunting has been reported by wild orangutans, what it does is report a longer-term observation of one hunting female, tying this case to earlier observations.

    I'm pointing to the paper because it includes some discussion about the requirements of meat eating for early hominins. These orangutans take a long time to chew up a slow lorus.

    Orangutans used more than twice the amount of time (160.9 g/h) to eat the same amount of meat than chimpanzees (348 g/h) (Wrangham 2009; Wrangham and Conklin-Brittain 2003). Other chimpanzee data shows that this species is able to consume meat at much higher rates, i.e., 1.9±1.2 kg/h (Gilby 2006). This difference between orangutans and chimpanzees may suggest that higher sociality in chimpan- zees influences intake rates, where individuals are surrounded by conspecifics when eating meat, and where meat is a highly preferred food item and stealing occurs (Boesch and Boesch 1989; Goodall 1986; Stanford 1999).

    I'll point out that orangutans may make a better model for early hominin jaw mechanics than chimpanzees do, because the sizes of jaw musculature and teeth are more comparable. Neither orangutans nor australopithecines have teeth that look well-made for reducing fibrous, tough meat into smaller pieces. Recent humans have been able to cook meat, which reduces its mechanical resistance to chewing. Early hominins didn't cook, so getting some high fraction of their caloric requirements from meat (even if only seasonally) might have taken a lot of time.

    According to orangutan data (ingestion rate of 185 kcal/h), Australopithecus africanus would have had to chew for ca. 2 h to achieve 25% of these caloric requirements purely from meat (Table III, orangutans×A. africanus), while achieving the remaining 75% of its caloric requirements from food sources with faster chewing/intake rates, e.g., leaves or insects. This constitutes a considerable period of the day for orangutans, which spend ca. 6 h/d feeding (Morrogh-Bernard et al. 2009), and does not include the time necessary for the collection of vertebrate prey.

    That sounds like a lot of chewing time, but it's not an insuperable barrier. The isotopic values for A. africanus and A. robustus suggest the possibility of up to 25% meat consumption, although they may have gotten C4 plant input by several different food sources (e.g., corms, edible stems, aquatic animals) as well as meat. Altogether, the chewing time analysis shuts off one line of argument that early hominins would have faced extreme constraints preventing them from moving to a more meat-intensive diet before the control and routine use of fire.

    References

    1. Hardus ME, Lameira AR, Zulfa A, Atmoko SUS, Vries H, and Wich SA. 2012. Behavioral, Ecological, and Evolutionary Aspects of Meat-Eating by Sumatran Orangutans (Pongo abelii). International Journal of Primatology.
    Tags: 
    orangutans
    diet
    apes
    hunting
    meat
    A. africanus
    Synopsis: 
    A discussion of early hominin meat-eating emerges from observations of orangutan hunting

  • A stretch of Bronze Age river

    Sun, 2011-12-04 14:41 -- John Hawks

    In the course of studying recent human evolution, I've done a lot of work on the skeletal remains of Bronze Age Europeans. This is a series of cultures we know vastly more about than Paleolithic people, but the occasional unique discovery can still bring striking information to light. The Guardian reports on a significant excavation going on near Cambridge, U.K.: "Bronze age man's lunch: a spoonful of nettle stew".

    The excavation, which is likely to continue for years, has been made possible thanks to Hanson, a bricks and cement supplier. Under planning regulations, the company is obliged to fund archaeological digs, but it has been especially helpful, say the archaeologists. Crucially, and unusually, they were able to excavate down to unprecedented depths since Hanson's need for clay for bricks requires extraction at Jurassic age levels. Knight said: "So we get to see entire buried landscapes. Some of our colleagues try to find ways of getting to the bottom of the North Sea… [while] we get an early view of the same submerged space, but via the humble brick."

    Along the 150-metre stretch of a bronze age river channel, they have found the best preserved example of prehistoric river life. There are weirs and fish traps in the form of big woven willow baskets, plus fragments of garments with ornamental hems made from fibrous bark and jewellery, including green and blue beads.

    The photo accompanying the story is remarkable, showing how a Bronze Age-era boat is excavated in stages. I find the weirs and fish traps among the most interesting parts, because we usually depend so strongly for our knowledge of food production practices on what will preserve for long periods of time. These aren't surprising, but finding a stretch of Bronze Age river channel with them in place gives us a much stronger perspective on their use, both then and possibly during earlier time periods.

    Tags: 
    Bronze Age
    Britain
    fish
    diet

  • Putting together australopithecine diets

    Sat, 2011-11-26 18:06 -- John Hawks

    Peter Ungar and Matt Sponheimer earlier this fall [1] reviewed the evidence for diet in early hominins, from both microwear studies (Ungar's specialty) and stable isotopes (Sponheimer's forté). I wanted to point to this article because it is a very useful short review that illuminates the cases in which these two sources of evidence lead to a single interpretation.

    [T]he isotope data also suggest enormous and unanticipated differences between contemporaneous taxa with strong morphological similarities, notably the “robust” australopiths P. robustus and P. boisei. Despite their attribution to the same genus, there is no overlap in their carbon isotope compositions (41), which is a rarity for congeners among extant mammals.

    Maybe this should give pause to those who insist that A. robustus and A. boisei are sister species. Ungar and Sponheimer here reiterate the observation that microwear is very similar between A. boisei and A. afarensis:

    The apparent continuity of microwear pattern through the putative lineage Au. anamensis–Au. afarensis–P. boisei could even suggest that morphological changes reflect increasing efficiency for grinding large quantities of tough food. Although living primates that eat tough items typically have sharp shearing crests, eastern African australopiths and especially P. boisei may have evolved a different solution for processing such foods, given the flattened, thickly enameled teeth of their close ancestors (23). Natural selection must work with the raw materials available to it. Thus, the present-day ecomorphological diversity within the primates may not be sufficient for making some paleoecological inferences, which is not surprising given that the vast majority of all primates, especially apes, that have ever lived are now extinct.

    This idea was raised earlier, for example in the context of the stable isotope findings on A. boisei ("'Nutcracker Man' debunked"). Until we have more stable isotope results from the known sample of A. afarensis or A. anamensis, we won't be able to test this "tough C4 food" hypothesis. "Ecomorphological diversity" refers to the match between food types and the topological properties of tooth crowns among living primates. Generally speaking, primates with high crowns and high cusp relief with shearing crests are thereby well-suited for eating tough foods like leaves and stems. That's the common ground between gorillas and colobines, for example. A. afarensis and especially A. boisei have exactly the opposite morphology from what would seem to be the "tough foods" pattern. So why do these species seem to be acting like grazers? Very peculiar.

    My own attitude is that if we can't clearly make sense of the anatomy of A. boisei, then we won't be able to untangle the diets of the other species. Early hominins evolved along a distinctive trajectory toward larger molars, smaller canines, and bigger jaw musculature within a common body plan. A. boisei represents the extreme of this trend. So if A. boisei is the logical morphological extreme, why does it seem to have such a different dietary strategy than every other hominin with stable isotope evidence?

    Meanwhile, if Ungar and Sponheimer are correct in asserting a common dietary strategy in the East African species, then it seems pretty clear that early Homo shares a dietary commonality with the South African species, not the East African ones. One might argue that Homo differentiated from other hominins within East Africa by adopting a fundamentally South African dietary strategy. But I would be more inclined to suppose a South African-derived hominin made incursions into East Africa, possibly repeated ones, as Homo was emerging. Ungar and Sponheimer are correct that natural selection works with the materials available. Population growth and migration are vastly more rapid than in situ evolution. What if the apparent "early Homo" record actually represents a series of successive dead-end migrations from southern Africa?

    References

    1. Ungar PS, and Sponheimer M. 2011. The diets of early hominins. Science (New York, N.Y.) 334:190-3.
    Tags: 
    diet
    A. boisei
    A. afarensis
    A. anamensis
    stable isotopes
    microwear
    Synopsis: 
    A review of microwear and stable isotope evidence of diet prompts questions about early hominin relationships.

  • Mailbag: Spuds and mutts

    Wed, 2011-11-09 00:28 -- John Hawks

    Re: "How widespread is Denisovan ancestry today?" and "Potato sack race":

    Question about Denisovan DNA. Once introduced into a population, beginning many millenia ago, what keeps it from being in the DNA of everybody in the area? I exclude new arrivals, but what kept the Denisovan DNA from being spread to the homeland of the new arrivals what with the traveling salesmen, the refugees from tribal pushing and shoving, armies marching, cross marching and countermarching? It isn't as if Denisovan genes cause assortative mating by making the possessor either a hell of a catch or a last-man-on-earth scenario. Is it? Selective survival against diseases that come and go, while not so good in between, a la sickle cell? Is the blender model of human reproduction faulty somehow.

    As to potatoes, I'd heard that one advantage is that armies, used to pasturing their horses in the grain of the enemy's peasants' fields, had to move on more quickly when the supply officers gave up trying to get their foraging parties to dig potatoes.

    If, as Keegan hypothesizes, the ration was one pound of meat and two of bread (requiring two pounds of firewood) per man per day, an army of 30,000 ate out a location pretty quickly. If spuds were the local staple, they'd have to move. You just can't feed 30,000 guests who arrived unannounced by digging potatos. Not fast enough. Do horses like potatos? So, the army moves on--win--and the peasants get out the potato forks and do okay, more or less. Win.

    Re: potatoes -- I think you've pointed to an important factor -- also, they can't be burned when the army retreats. The sheer productivity of tubers really does outweigh the available grain crops in Northern Europe.

    Re: Denisovan DNA -- The genes should have diffused into other populations, all things being equal. That they did not do so is a pretty strong indication that SE Asia today shares little genetically with SE Asia 30,000 years ago. There must have been a massive influx of people who lacked Denisovan ancestry, well after the initial mixture with Denisovans happened and Denisovans themselves left the scene.

    Tags: 
    mailbag
    diet
    agriculture
    Denisova
    admixture
    population structure
    introgression

  • Potato sack race

    Fri, 2011-10-28 14:30 -- John Hawks

    Smithsonian magazine has a very nice article by Charles C. Mann, "How the Potato Changed the World", focusing on the effects of the Columbian exchange on Europe.

    “For the first time in the history of western Europe, a definitive solution had been found to the food problem,” the Belgian historian Christian Vandenbroeke concluded in the 1970s. By the end of the 18th century, potatoes had become in much of Europe what they were in the Andes—a staple. Roughly 40 percent of the Irish ate no solid food other than potatoes; the figure was between 10 percent and 30 percent in the Netherlands, Belgium, Prussia and perhaps Poland. Routine famine almost disappeared in potato country, a 2,000-mile band that stretched from Ireland in the west to Russia’s Ural Mountains in the east. At long last, the continent could produce its own dinner.

    When I toured through the Altai this summer, I was impressed at the healthy potato patch outside nearly every house. How unlikely it seems that this American crop should have become a central part of people's lives in some of the most remote parts of Central Asia.

    Tags: 
    agriculture
    domestication
    diet
    history
    America
    Europe

  • The diet of Gigantopithecus

    Wed, 2011-10-26 13:07 -- John Hawks
    Synopsis: 
    Gigantopithecus was once imagined as an exclusive bamboo feeder, but evidence suggests a broader diet focused on fruits

    Gigantopithecus has often been described as a bamboo eater, based on analogy with another kind of large herbivore in China, the giant panda. Giant pandas have several specialized feeding adaptations to support their bamboo diet. The most famous of these is the expansion of what we would call a wrist bone in most mammals, a sesamoid bone associated with the distal radius. In giant pandas, this bone projects from the arm in a way that makes it function similar to an additional digit for the hand, a solution described as "the panda's thumb". This "thumb" is used to grip the bamboo stems so that the teeth can work through the indigestible fiber and woody portions of the bamboo stems into the softer shoots. As a famous example in the history of evolutionary biology, the panda's thumb was celebrated by the evolutionary biologist Stephen Jay Gould as a unique evolutionary solution.

    Some information on the dietary proportions of giant pandas is available from BBC News. The following is quoted from that site:

    Ninety nine per cent of a panda's diet is made up of 30 species of bamboo. The remaining one per cent is made up of other plants and meat. Their digestion of bamboo is very inefficient; pandas only digest about 20 per cent of the dry matter of bamboo, whereas most herbivores assimilate about 80 per cent. This means that they must eat large amounts to obtain their energy requirements. They can eat between 12 and 38kg of bamboo shoots, leaves and stems per 24 hour period.

    Giant pandas can maintain this dietary solution only by sustaining a high feeding rate. The digestibility of bamboo varies markedly across the year (Wei et al. 1999), and in the winter when new growth is rare or absent, there are very few nutrients available. Pandas do not have any significant digestion of the structural elements of cell walls or other fibers. They therefore must extract the proteins and simple carbohydrates from bamboo and pass the bulk as quickly as practicable. To this end, they have wide and flat molars and premolars compared to other bears. These are not teeth with high crowns and shearing surfaces. This makes them different from primates, like gorillas and colobus monkeys, that eat a high proportion of leaves and other vegetation. It seems that pandas are not really in the business of cutting fibrous bamboo into a pulp; but instead they crush the bamboo to extract as much of the cell contents as possible.

    Gigantopithecus also had broad, flat molars and premolars. These teeth had relatively thick enamel. Enamel thickness is a tricky indicator of diet, because there are actually advantages to having enamel that wears through completely during life. If the goal is to maintain an effective shearing surface on the tooth for cutting fibrous plant material, then thin enamel exposes the softer dentin, which wears faster. The wear gradient between the two maintains a topography to the tooth surface that is a better shearing implement than a flat, thick-enameled tooth. So the thick molar enamel in Gigantopithecus would not be very useful for shearing bamboo leaves into an undifferentiated mush. But those teeth might have been used to crush bamboo to extract the cell contents while leaving the mass mostly intact.

    The evidence suggests that Gigantopithecus differed from giant pandas in having a more varied diet. One of the world's experts on Gigantopithecus is the paleoanthropologist Russ Ciochon. He has
    a very nice article about the species which appeared in Natural History magazine in 1991. This nice review features the history of Gigantopithecus discoveries, our current understanding of their anatomy, diet, and history, and Ciochon's own attempts to find fossil Gigantopithecus in Vietnam.

    Ciochon describes looking for phytoliths on the teeth as evidence of diet. When the fossil teeth of Gigantopithecus were examined with scanning electron microscopy, dozens of phytoliths were found:

    More than half of the phytoliths we observed were long and needlelike and could be attributed to the vegetative part of grasses, possibly bamboo. The rest were conical or hat shaped, attributable to the fruits and seeds of dicotyledons. Piperno tentatively identified them as fruits from a tree of the family Moraceae, quite possibly durian or jackfruit, both of which are common throughout tropical Southeast Asia. This proved that Gigantopithecus had a varied diet, although we still suspect that bamboo was its staple food.

    This work is described in
    Ciochon et al. (1990) in PNAS, which includes scanning electron micrographs of the phytoliths.

    Of course the relative quantities of phytoliths do not directly address dietary composition, since different plants have different phytolith abundances. Likewise, one might speculate that the phytoliths on fossil teeth represent foods eaten near the time of death -- a "last meal" effect. This might explain the apparent evidence for one kind of fruit in the Gigantopithecus data: the individual died at the time that fruit was in season. In any event, Ciochon and colleagues (1990) conclude it likely that Gigantopithecus had a very broad diet, that nonetheless included bamboo as a staple. In support of this, they cite an examination of tooth wear by Daegling and Grine (1989 in abstract; later published in 1994 in SAJS) that found Gigantopithecus microwear to be similar to chimpanzees. Chimpanzees themselves eat a majority of fruit, with smaller proportions of leaves, insects, and meat.

    References:

    Wei F, Feng Z, Wang Z, Zhou A and Hu J. 1999. Use of the nutrients in bamboo by the red panda (Ailurus fulgens). J Zool Lond 248:535-541.

    Ciochon RL, Piperno DR and Thompson RG. 1990. Opal phytoliths found on the teeth of the extinct ape Gigantopithecus blacki: implications for paleodietary studies. Proc Natl Acad Sci U S A 87:8120-8124.
    JSTOR

    Dean MC and Schrenk F. 2003. Enamel thickness and development in a third permanent molar of Gigantopithecus blacki. J Hum Evol 45:381-387.

    Daegling DJ and Grine FE. 1994. Bamboo feeding, dental microwear, and diet of the Pleistocene ape Gigantopithecus blacki. S Afr J Sci 90:527-532.

    Ungar P. 1998. Dental allometry, morphology and wear as evidence for diet in fossil primates. Evol Anthropol 6:205-217.

    Study terms: 
    Gigantopithecus
    phytolith
    sesamoid
    Tags: 
    diet
    Gigantopithecus
    Miocene
    Miocene ape evolution
    China

  • Mailbag: Humans are predators

    Tue, 2011-09-20 11:42 -- John Hawks

    Re: Shellfish

    I have been following your weblog for a while and just read your weblog on shellfish diet of early hominines. Interesting.

    I have a little question that you – hopefully – may be prepared to answer:

    Anthropologists describe our ancestors often as “hunters and gatherers”.

    You do that too in your blog. Actually, you do that quite often. It is obviously a valid paradigm.

    Humans are often further characterized as “Predators” which I consider a strange term for primates.

    Well, I see an abundance of evidence – including your blog entry above – that contradicts this characterization.

    I do not see much evidence that supports it.

    Actually, I do not know of any supporting evidence at all.

    The commonly named observations, scratched bones and hunting chimps, only verify that some bones have been scratched (by humans or natural processes?) and that chimps can spend their lives successfully as hunters as long as scientists with Doctor’s cases stand nearby to help them survive the risks of otherwise deadly infections.

    I saw that the diet question is your topic as a scientist.

    So, you may have strong evidence?

    I wonder if this is a confusion of language? A predator is an animal that kills and eats other animals. Any hunter is by definition a predator.

    That does not preclude other means of subsistence or other trophic relationships with different species. Humans were predators from at least 2.5 million years ago, but they were also prey animals of lions, sabretooths and hyenas for most of that time.

    I see your reference to chimpanzee hunting. Chimpanzees hunt in every population where they have been observed in the wild, and new field sites have invariably found them already hunting. There is no need for doctors among them. Many primates are predators, it is not strange at all. Small nocturnal primates obtain most of their caloric requirements from predation of insects and other small animals.

    Tags: 
    diet
    predation
    shellfish
    hunting

  • Shellfish gathering, paleoanthropological strawman

    Sun, 2011-09-18 15:26 -- John Hawks

    We have known for many years that Lower Paleolithic people were using shellfish, fish, and littoral resources at sites across the Old World, from Trinil [1], Koobi Fora [2], Gesher Benot Ya'aqov [3], and elsewhere. I've discussed the evidence several times (maybe most usefully in "The shells of Trinil"). As I wrote last year ("Fishy story at Koobi Fora"):

    Aquatic animals aren't important because of their sheer numbers, but because they tell us about the flexibility of foraging behavior. Living hunter-gatherers eat turtles and reptiles when they can, and because they are usually small food packages, they often eat them where they find them instead of returning to a base camp first. Hunter-gatherers are flexible in what they eat and where they eat it. FwJj20 is showing at least a substantial taxonomic flexibility in the meat-eating of early Oldowan hunters.

    So why do we keep seeing stories that make shellfish consumption look like news when it's done by Neandertals, MSA Africans, or anybody else?

    I'm writing about this today because of a new paper in PLoS ONE by Miguel Cortés-Sánchez and colleagues, reporting on the shellfish remains in Bajondillo Cave, Spain [4].

    Shellfish collecting has been well characterized in some Mousterian contexts. Mary Stiner treated it systematically in her 1993 monograph, Honor Among Thieves, which is part of the graduate education of most young Paleolithic archaeologists. Stiner spent a lot of text quantifying shellfish use and gave a good discussion of the biases that make archaeologists find less evidence of shellfish consumption than there probably was.

    Most important, when you can walk along a shoreline and nosh shells, you're not very likely to haul many of them back to a cave several kilometers from the shore. In the Holocene, we find lots of archaeological localities where people were systematically collecting many shells and cooking them for large groups. For this purpose, the people carried baskets or sacks of shellfish for a good distance, and after they were consumed, the shells sometimes built up into large trash piles, or middens. We don't see shell middens in Mousterian or MSA contexts, but then we see very little of that kind of behavior with any kind of resources in MSA or Mousterian times. Here's what I wrote in 2008 ("Neandertal diet was not dolphin safe"):

    [I]t was hard to understand the excitement that accompanied last year's paper by Curtis Marean and colleagues (2007), who found evidence for shellfish exploitation at Pinnacle Point, South Africa. The press reported the result as if there were a shell midden, with abundant evidence for consumption. But actually the number of shells is fairly small -- all the shells from all the layers reported weigh less than a kilogram. That looks similar to the pattern of exploitation that Stiner had reported for the Neandertals at Moscarini, and more or less like the pattern at Vanguard and Gorham's Caves.

    The African MSA-era site with the most direct evidence of shellfish exploitation is at Abdur, Eritrea, where the stone tools are found in an ancient shore terrace, presumably at the very place where shellfish exploitation was happening [5]. That paper hinted at even earlier sites with similar evidence from Acheulean contexts along the Red Sea rift, where subsidence of the rift floor has left some ancient coral reefs exposed, Acheulean tools embedded within them. I should also point out indirect evidence on the basis of species abundance for human exploitation of giant clams in the Red Sea ("The ancient struggle for existence between humans and giant clams").

    In other words, archaeologists have found quite a lot of evidence of coastal resource use by early people, despite the steep biases against it. In the case of aquatic animal exploitation, they've got it as early as the Oldowan, 1.95 million years ago [2].

    Cortés-Sánchez and colleagues [4] add detail to this record but don't really broaden the picture. Mousterian shellfish acquisition around 150,000 years ago, well before the last interglacial, is earlier than many well-known instances of MSA shellfish utilization. But we know that much earlier humans were using these coastal resources, so it's hardly news. As at other sites, the mollusc remains are not very dense: a minimum of 16 shells in one layer, 66 shells in another, 80 in a third. If I were going to make a story out of it, I would direct more attention to the pearl, first I've ever heard of in a Neandertal site.

    More important is the paper's demonstration that humans actually processed the shells. Cortés-Sánchez and colleagues contrast the condition of continental and marine molluscs in the same levels, to show the systematic breakage and burning of the marine species:

    [A]lmost all of the marine mollusks exhibit intensive mechanical fracturing, with sharp edges on their shells suggestive of an absence of post-depositional transport, and very few appear complete (i.e., barely 7% at Bj19). Such fracturing, coupled with the absence of shells eroded by water, indicates that the marine mollusks from Bajondillo Cave, and in particular those from Bj19 do not represent “background fauna” from the nearby beach, a phenomenon that has recurrently caused problems in the association of early Middle Paleolithic shellfish deposits from the Mediterranean with paleo-human activities. In addition, a substantial percentage of the mussels exhibit burning marks (Figure 4: 1–6). These are recorded on 48% of the adult specimens from Bj19, the young mussels never exhibiting such traces. Thermo-alterations suggest consumption rather than passive burning, given that in most cases only the outer portions of the shells appear carbonized and/or flaked. An indirect line of evidence supporting this same hypothesis is provided by five of the epibiont barnacle remains that fire not only detached from the mussel shells but that in that process were thoroughly carbonized, as is the case of the four specimens from Bj18 (Figure 4: 8,11) or else calcined, as happens with the specimen from Bj19 (Figure 4: 12).

    I appreciate the paper's list of 24 previously-published Neandertal sites that present mollusc remains. It would be useful to compile a broader list including MSA sites. Personally, I hope to never read again a headline about how surprising or significant was shellfish use by early humans.

    References

    1. Joordens JCA, Wesselingh FP, de Vos J, Vonhof HB, and Kroon D. 2009. Relevance of aquatic environments for hominins: a case study from Trinil (Java, Indonesia). Journal of Human Evolution 57:656-71.
    2. Braun DR, Harris JWK, Levin NE, McCoy JT, Herries AIR, Bamford MK, Bishop LC, Richmond BG, and Kibunjia M. 2010. Early hominin diet included diverse terrestrial and aquatic animals 1.95 Ma in East Turkana, Kenya. Proceedings of the National Academy of Sciences of the United States of America 107:10002-7.
    3. Alperson-Afil N, Sharon G, Kislev M, Melamed Y, Zohar I, Ashkenazi S, Rabinovich R, Biton R, Werker E, Hartman G, et al. 2009. Spatial Organization of Hominin Activities at Gesher Benot Ya'aqov, Israel. Science [Internet] 326:1677–1680. Available from: http://dx.doi.org/10.1126/science.1180695
    4. Cortés-Sánchez M, Muñiz A, Simón-Vallejo ía D, Lozano-Francisco ía C, Vera-Peláez JL, Finlayson C, Rodríguez-Vidal J, Delgado-Huertas A, Jiménez-Espejo FJ, Martínez-Ruiz F, et al. 2011. Earliest Known Use of Marine Resources by Neanderthals. PLoS ONE 6:e24026.
    5. Walter RC, Buffler RT, Bruggemann JH, Guillaume MM, Berhe SM, Negassi B, Libsekal Y, Cheng H, Edwards RL, von Cosel R, et al. 2000. Early human occupation of the Red Sea coast of Eritrea during the last interglacial. Nature 405:65-9.
    Tags: 
    shellfish
    diet
    Neandertals
    Middle Paleolithic
    Mousterian
    MSA
    modern
    behavior
    foraging
    aquatic resources
    Synopsis: 
    Why do archaeologists always make shellfish gathering sound like news, when we know it's not surprising?

  • "Nutcracker Man" debunked

    Tue, 2011-05-03 00:44 -- John Hawks

    This week, Thure Cerling and colleagues report in PNAS [1] carbon stable isotope data from 24 specimens of Australopithecus boisei. This is a huge sample as fossil hominins go, and they give a very consistent picture about the diet of this most robust of the australopithecines. These 24 individuals got between 61 and 91 percent of their carbon from grasses.

    My 2005 explainer on stable isotope chemistry and early hominin diets fills in the details about carbon-12, carbon-13 and their relationship to 3- and 4-carbon photosynthetic cycles. The salient aspect of the comparisons involving A. boisei here is that C4 plants, mostly grasses, incorporate relatively more carbon-13 than do other plants, and herbivores assimilate this carbon-13 into their bones and teeth.

    The high ratio of grass-derived carbon in A. boisei is fundamentally different from all living and fossil apes, and it is far higher than the values found for other early hominins. The only other primate that comes close is the fossil giant gelada Theropithecus oswaldi, a savanna-living species.

    What were these extinct species really eating? Was grass the food? For living geladas, grass consumption includes seeds -- a fact that led Clifford Jolly to suggest that early hominins might also have specialized on seeds [2]. Of course, humans today also specialize on grass seeds. We call them grains, eat them in bread and drink them in soda. And beer.

    But what about A. boisei? The large, thick-enameled premolars and molars, with their low cusps, seem well suited to grinding small hard objects and resisting the resulting wear. But Cerling and colleagues devote a good chunk of their discussion to the description of molar wear in A. boisei and other early hominins. Their argument is that the teeth of A. boisei show no signs of "hard object" feeding:

    Of perhaps greater moment than its potential specific simila- rities, the microwear of P. boisei molars, which shows remarkable uniformity over time from about 2.3 Ma to about < 1.4 Ma (9, 24), stands in stark contrast to the wear fabrics exhibited by primate hard-object consumers. Indeed, there is no evidence beyond the anecdotal [e.g., the broken left first permanent molar crown in the KNM-ER 729 P. boisei mandible (8) and the observation that a couple of P. boisei molars show antemortem enamel chipping (25)] that these food items were hard.

    These observations are not new, but putting them together with the evidence of grass consumption makes it pretty clear that seed eating was not a predominant source of dietary carbon. The "Nutcracker Man" sobriquet, applied to A. boisei because of its powerful jaw mechanics, must be false. No significant hard object feeding, very low dietary carbon from trees and non-grassy (or sedgy) plants.

    Instead, Cerling and colleagues propose that both A. boisei and other early hominins wore their teeth on the, well, grassy parts of grass.

    P. boisei cheek teeth display notable gradients of gross wear, resulting in large, deeply excavated dentine exposures, and in this regard, they are similar to other australopith species (e.g., A. afarensis and A. africanus) that also possess low tooth cusps with thick enamel. Thus, like other australopiths, P. boisei undoubtedly had a diet that consisted of foods with abrasive qualities—the gross wear is as likely due to repetitive loading of phytolith-rich tough foods as exogenous grit. Thus, either grass or sedge consumption and/or exogenous grit might well have contributed to P. boisei’s notable wear gradient.

    And:

    Recent dental microwear studies suggest that the mechanical properties of A. afarensis (and A. anamensis) diets were nearly identical to those of P. boisei (9, 24, 40–42). If this is so, could it be that the australopith masticatory package represents an adaptation to C4 resources such as grasses or sedges? The similarity in dental microwear fabrics among the eastern African australopiths, all of which lack any evidence for hard-object food consumption (9, 24, 40–42), is consistent with the notion that their craniodental morphology could reflect “repetitive loading” rather than hard-object consumption (7, 8, 43).

    Grit might get in from eating underground parts like rhizomes. Phytoliths are small, hard silicate structures in the green parts of plants, including the stems and leaves of grass.

    Last year I wrote about carbon isotope analysis of two specimens of Australopithecus boisei, the famous OH 5 "Zinj" specimen, and the Peninj mandible. Both specimens show evidence of a high consumption of grass-derived carbon -- estimated at 77% and 81% grass-derived carbon, respectively. Those levels are characteristic of grazing animals. Cerling and colleagues show that these values are right in the middle of the range among specimens of A. boisei that cover a half million years in Kenya and Tanzania.

    In the paper reporting the carbon stable isotopes of OH 5 and Peninj, van der Merwe and colleagues [3] suggested that A. boisei may have relied on papyrus as a staple. The culms and rhizomes of papyrus both have substantial nutritional content but are very fibrous and require much chewing and spitting out fiber at intervals. The hypothesis would imply that A. boisei relied on these foodstuffs for the majority of its calories.

    Cerling and colleagues do not mention papyrus, and take a much more direct approach on grass-eating. But they do report data on oxygen stable isotopes from the specimens that may be relevant to the ecological context of grass (or sedge) consumption. Oxygen isotopes in bone and teeth reflect the pattern of water consumption by an animal. Oxygen-16 evaporates and transpires preferentially from leaves, so an animal living in an arid environment that gets most of its water from plants will be relatively enriched for the heavier oxygen-18. An animal that depends on drinking water from lakes or rivers will tend to have lower oxygen-18. A. boisei is almost as low in oxygen-18 composition as hippopotamus, suggesting they were strongly dependent on water sources.

    A highly water-dependent grass-eating A. boisei is a very different picture of the biology of this robust species. The South African robust species, A robustus, is very different in this regard. These two species are often lumped together, but this is unfair in many ways to their distinctive anatomical patterns. Knowing that their dietary adaptations were very distinct, we should be more inclined to focus on the details where they differ.

    Bottom line: A. boisei represents a highly distinctive dietary pattern, not present in any living ape, that no longer exists. At least the giant gelada, T. oswaldi, may also have exploited similar resources. Some grass resources, including papyrus corms and rhizomes, have high caloric and nutritional value, but require adaptations to deal with the fibrous content.

    References

    1. Cerling TE, Mbua E, Kirera FM, Manthi FK, Grine FE, Leakey MG, Sponheimer M, and Uno KT. 2011. Diet of Paranthropus boisei in the early Pleistocene of East Africa. Proceedings of the National Academy of Sciences [Internet] 108:9337–9341. Available from: http://dx.doi.org/10.1073/pnas.1104627108
    2. Jolly CJ. 1970. The seed eaters: a new model of hominid differentiation based on a baboon analogy. Man 5:5–26.
    3. van der Merwe NJ, Masao FT, and Bamford MK. 2008. Isotopic evidence for contrasting diets of early hominins Homo habilis and Australopithecus boisei of Tanzania. South African Journal of Science [Internet] 104:153–155. Available from: http://www.scielo.org.za/scielo.php?pid=S0038-23532008000200016&\#38;script=sci\_arttext&\#38;tlng=en
    Tags: 
    Early Pleistocene
    Koobi Fora
    Tanzania
    A. boisei
    diet
    Kenya
    Olduvai Gorge
    A. robustus

  • Mailbag: Thick skulls and diet

    Tue, 2011-04-12 23:15 -- John Hawks

    Re: "Hard headed science":

    Although genetics undoubtedly play a part in the thickness of the skull bone, there is another parameter that more often than not is overlooked by anthropologists. That parameter is nutrition. Modern man is overfed on calories but malnourished on micronutrients. Soft tissues always evolve to their fullest, but the hard tissues, i.e. bone, are much more dependent on nutrition and physical work-load. Compared to the skulls of its ancestors, the skull of modern man is thinner, smaller, narrower, the eye sockets tend to be rounder and there tends to be insufficient space for the teeth in the mouth. It seems reasonable to me that in so far as the shape of the skull, it is the phenotype that’s changed, not the genotype.

    Nutrition can make a difference, but the variation in skull thickness during the last 2 centuries is very minor compared to the amount of difference between Homo erectus, Neandertals and us. The thinning also preceded any significant shift from hunting and gathering to agriculture. There has been further thinning after agriculture, so that we can't attribute the shift to a straightforward diet change.

    Tags: 
    Homo erectus
    paleopathology
    nutrition
    diet

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