‘Lucy’ could climb like chimps, some modern humans too

The transition from an arboreal lifestyle to a purely terrestrial one was never finished: some modern humans who live natural lifestyles in the forests of Earth still climb more or less like a chimpanzee, i.e. “walking” vertically.

This seems more a matter of acquired flexibility of certain calf muscles than anything else (although I imagine that a small complexion, which reduces weight, may also help a lot).

Emphasis is made therefore in that australopithecines like Lucy, who had clear anatomical adaption to walk like we do, could still be using trees almost at whim: there’s no such a binomial disjunctive between walking and climbing and wide compromises can be made.

Vivek V. Venkataraman, Tree climbing and human evolution. PNAS, 2010. Open access → LINK [doi: 10.1073/pnas.1208717110].

Abstract

Paleoanthropologists have long argued—often contentiously—about the climbing abilities of early hominins and whether a foot adapted to terrestrial bipedalism constrained regular access to trees. However, some modern humans climb tall trees routinely in pursuit of honey, fruit, and game, often without the aid of tools or support systems. Mortality and morbidity associated with facultative arboreality is expected to favor behaviors and anatomies that facilitate safe and efficient climbing. Here we show that Twa hunter–gatherers use extraordinary ankle dorsiflexion (>45°) during climbing, similar to the degree observed in wild chimpanzees. Although we did not detect a skeletal signature of dorsiflexion in museum specimens of climbing hunter–gatherers from the Ituri forest, we did find that climbing by the Twa is associated with longer fibers in the gastrocnemius muscle relative to those of neighboring, nonclimbing agriculturalists. This result suggests that a more excursive calf muscle facilitates climbing with a bipedally adapted ankle and foot by positioning the climber closer to the tree, and it might be among the mechanisms that allow hunter–gatherers to access the canopy safely. Given that we did not find a skeletal correlate for this observed behavior, our results imply that derived aspects of the hominin ankle associated with bipedalism remain compatible with vertical climbing and arboreal resource acquisition. Our findings challenge the persistent arboreal–terrestrial dichotomy that has informed behavioral reconstructions of fossil hominins and highlight the value of using modern humans as models for inferring the limits of hominin arboreality.

See also: Science Daily. H/t Pileta[es].

 

Eastern Pygmies are not L1

Just a brief note to account for a paper to which I do not have access to but that says openly in the abstract that mtDNA lineages of Western and Eastern Pygmies are different.

It says that, while West Pygmies are essentially in the L1c haplogroup, Eastern Pygmies are instead in the L0a, L2 and L5 clades.

Chiara Battinin et al., Insights into the demographic history of African Pygmies from complete mitochondrial genomes. Molecular Biology and Evolution 2010. Pay per view.

Abstract

Pygmy populations are among the few hunter-gatherers currently living in sub-Saharan Africa and are mainly represented by two groups, Eastern and Western, according to their current geographical distribution. They are scattered across the Central African belt and surrounded by Bantu-speaking farmers, with whom they have complex social and economic interactions. To investigate the demographic history of Pygmy groups, a population approach was applied to the analysis of 205 complete mitochondrial DNA (mtDNA) sequences from ten central African populations. No sharing of maternal lineages was observed between the two Pygmy groups, with haplogroup L1c being characteristic of the Western group, but most of Eastern Pygmy lineages falling into sub-clades of L0a, L2a and L5. Demographic inferences based on Bayesian coalescent simulations point to an early split among the maternal ancestors of Pygmies and those of Bantu-speaking farmers (∼70,000 ya, years ago). Evidence for population growth in the ancestors of Bantu-speaking farmers has been observed, starting ∼65,000 ya, well before the diffusion of Bantu languages. Subsequently, the effective population size of the ancestors of Pygmies remained constant over time and ∼27,000 ya, coincident with the Last Glacial Maximum, Eastern and Western Pygmies diverged, with evidence of subsequent migration only among the Western group and the Bantu-speaking farmers. Western Pygmies show signs of a recent bottleneck 4,000 – 650 ya, coincident with the diffusion of Bantu languages, while Eastern Pygmies seem to have experienced a more ancient decrease in population size (20,000 – 4,000 ya). In conclusion, the results of this first attempt at analysing complete mtDNA sequences at the population level in sub-Saharan Africa not only support previous findings but also offer new insights into the demographic history of Pygmy populations, shedding new light on the ancient peopling of the African continent.

Found at Dienekes’.

Related posts at Leherensuge (my old blog):

• The early expansion of H. sapiens in Africa (mtDNA)
• Study suggests single origin for Pygmies (notice that both populations are clearly different already at K=3 anyhow)