Saturday, February 29, 2020

Evolution of the Human Foot

Nature News has an interesting examination of how the human foot evolved the arch, the singular most important aspect in the ability to perform bipedal locomotion.  Glen Lichtwark and Luke Kelly write:
Humans evolved to walk and run effectively on the ground using two feet. Our arched foot, which is not a characteristic of other primates, is a unique feature crucial for human bipedalism. The arch provides the foot with the stiffness necessary to act as a lever that transmits the forces generated by leg muscles as they push against the ground. The arch also retains sufficient flexibility to function like a spring to store and then release mechanical energy. Writing in Nature, Venkadesan et al.1 present a new view of how foot stiffness is regulated. Their finding not only has exciting implications for understanding foot evolution, but also provides a possible framework when considering foot health and how to design better footwear.
The authors note that there are two different arches present in the human foot, the longitudinal arch, which is more familiar to people and the transverse arch. They argue that the transverse arch (across the top of the foot) is as important for walking as the longitudinal arch. The authors note that the transverse arch has been neglected in sports and medicine and that more research needs to be done in this area. 

Thursday, February 27, 2020

Humans in Asia survived Toba super-eruption 74,000 years ago

Chris Clarkson and company have produced a study arguing that the super volcano Toba eruption of 74,000 years ago did not lead to a population bottleneck in Asia, as has been suggested.  Brook Hays of UPI writes:
For the study, scientists analyzed evidence of human populations and climate change across a significant stratigraphic record -- a column of rock and sediment layers comprising 80,000 years of history -- from the Dhaba dig site in northern India's Middle Son Valley.

The column yielded stone artifacts suggesting Middle Palaeolithic tool-using populations were present in India prior to the Toba eruption.

"Although Toba ash was first identified in the Son Valley back in the 1980s, until now we did not have associated archaeological evidence, so the Dhaba site fills in a major chronological gap," researcher J.N. Pal, professor of ancient history and archaeology at the University of Allahabad in India, said in a news release.
The authors argue that there are stone tools at the Dhaba site the strongly resemble Middle Stone Age tools in Northeast Africa. The occupation levels go down to 48,000 years ago, where Levallois and microlithic tools are found. This suggests continuous occupation of the site by different groups with similar stone tool technologies.

Time to chuck another theory into the dustbin of history.  

Thursday, February 13, 2020

The Ghost of an Unknown Hominin

Science Alert has a story about the Ghost of an Unknown Hominin in Africa.  Carly Cassella writes:
The gene pool of modern West Africans contains the 'ghost' of a mysterious hominin, unlike any we've detected so far. Similar to how humans and Neanderthals once mated, new research suggests this ancient long-lost species may have once mingled with our ancestors on the African continent.

Using whole-genome data from present-day West Africans, scientists have found a small portion of genetic material that appears to come from this mysterious lineage, which is thought to have split off from the human family tree even before Neanderthals.
It is not clear to me that these necessarily represent different species. This may reflect an inter-related group of populations from a very genetically diverse population. As my advisor Fred Smith once upon a time said: “If two species interbreed on a regular basis, is it reasonable to call them different species?”

BTW, the  “Unrelated” skull in the page is the Kabwe skull from What was once Rhodesia, discovered in 1925, 400 feet down, in a mine.

Thursday, February 06, 2020

BBC: How Did the Last Neanderthals Live

The BBC has a post on some archaeological discoveries that have illuminated how the Neandertals lived.  Melissa Hogenboom writes:
For the most part, Neanderthals were a resilient group. They existed for about 200,000 years longer than we modern humans (Homo sapiens) have been alive. Evidence of their existence vanishes around 28,000 years ago – giving us an estimate for when they may, finally, have died off.

Fossil evidence shows that, towards the end, the final few were clinging onto survival in places like Gibraltar. Findings from this British overseas territory, located at the southern tip of the Iberian peninsula, are helping us to understand more about what these last living Neanderthals were really like. And new insights reveal that they were much more like us than we once believed.
It always seems to strike these writers as odd that Neandertals were capable of culture roughly equivalent to our own.  The last group of Neandertals lived at a time that was much harsher, climate-wise, than today, with the tundra line being equivalent in latitude, to Vienna.

The original Gibraltar skull was discovered in 1848 (eight years before the type specimen was discovered in the Neander Valley, in Germany).  Clive Finlayson, the Director of the Gibraltar Museum has been part of a team that has been excavating the set of caves there and four caves have been identified.
“It was in some way Neanderthal city,” he says. “This was the place with the highest concentration of Neanderthals anywhere in Europe.” It’s not known if this might amount to only dozens of people, or a few families, since genetic evidence also suggests that Neanderthals lived in “many small subpopulations.”
There is still considerable mystery surrounding just why the Neandertals faded out. The best theory going at the moment is gene swamping. Given that the Neandertal and early modern human genomes were both probably pretty stable, Neandertal/modern human mating could very well have resulted in hybrid depression. Eventually, the Neandertal genes, facing negative selection, dropped out of the genome.