Thursday, March 07, 2019

More Information From Denisova

Nature News is reporting about some more evidence from Denisova, following up on the bombshell news last year that bones discovered there belonged to a person (who they named “Denny”) who's father was a Denisovan and mother a Neandertal. From the story:
In the years that followed the discovery of Denisovans, scientists used DNA sequencing to attribute a few molar teeth from the cave to the same group4. They have also found other remains that harboured Neanderthal DNA. The analysis of Denny fills in some important details about the two groups. “We knew that Denisovans and Neanderthals had been there. We just didn’t think they interacted this intimately,” says [Svante] Pääbo. “It was so amazing to find direct proof — to find these people in the act, almost, of mixing.”

Denny’s discovery has also convinced Pääbo and other scientists that the remains of similar individuals, with recent ancestry from two groups of hominin, will be found — perhaps also in Denisova Cave. Researchers who analysed Denny’s genome found signs that the chromosome set that was contributed by her father, although clearly Denisovan, harboured some Neanderthal ancestry, which hints at earlier encounters between the groups2. “We should be able to pick up these individuals,” says [Katerina] Douka.
The Denisova cave appears to have been occupied for several hundred thousand years, being originally settled by either Denisovans or Neandertals, no one is sure which. Subsequent to this, it is unclear how much interbreeding actually occurred. 
“It’s still a head scratcher,” adds Tom Higham, an archaeological scientist at the University of Oxford, UK, who works with Douka and Brown. “It’s either an incredible piece of luck, or interbreeding happens so frequently that we might expect to find these types of occurrence in the archaeological record.”
One thing becomes increasingly clear with each new discovery, however: the complete replacement model of modern human origins, as espoused by Stringer and Andrews, is dead.

Tuesday, March 05, 2019

More Evidence For Bipedality at 4.5 MYA

Out of Case Western Reserve comes a study of some new fossil material that sheds like on early human bipedal adaptation.  From ScienceDaily:
Scott W. Simpson, PhD, led an analysis of a 4.5 million-year-old fragmentary female skeleton of the human ancestor Ardipithecus ramidus that was discovered in the Gona Project study area in the Afar Regional State of Ethiopia.

The newly analyzed fossils document a greater, but far from perfect, adaptation to bipedalism in the Ar. ramidus ankle and hallux (big toe) than previously recognized. "Our research shows that while Ardipithecus was a lousy biped, she was somewhat better than we thought before," said Simpson.
While the weight of evidence has always a bit more than slightly favored the facultative bipedality of Ardipithecus ramidus, this research provides greater support for this hypothesis.  In my class, I stress the difference between facultative bipedality (practiced by Ardipithecus) and obligate bipedality (practiced by every other hominin).  Additionally, from the article1:
The more complete adoption of bipedality in the australopiths resulted in the loss of functionally critical adaptations to arboreality present in Ardipithecus such as a grasping, opposable hallux, an antero-posteriorly broad pelvis with reorganization of the origin (and most likely function) of the hamstring muscles, and a more derived humero-femoral ratio. The changes in the size and structure of the dentition in the subsequent australopiths (larger molar and premolar crowns, increased enamel thickness, more robust mandibles) indicates a major behavioral and dietary shift for most hominins (perhaps excluding the species indicated by the Burtele foot) that occurred about 4.2 Ma with the earliest appearance of Australopithecus (Leakey et al., 1995, White et al., 2006).
Many of these changes, then, appear to have occurred somewhat rapidly, once the early hominins moved away from the forest and into the fringe.  Once we thought that bipedality originated in the forest/fringe.  The Ardipithecus data have killed this hypothesis. 

1Scott W. Simpson, Naomi E. Levin, Jay Quade, Michael J. Rogers, Sileshi Semaw. Ardipithecus ramidus postcrania from the Gona Project area, Afar Regional State, Ethiopia. Journal of Human Evolution, 2019; 129: 1 DOI: 10.1016/j.jhevol.2018.12.005

Monday, March 04, 2019

Neandertals Had Same Gait as Modern Humans

A virtual reconstruction of the skeleton of the La Chapelle Neandertal has revealed that Neandertals had exactly the same bipedal pattern that modern humans had.  From the ScienceDaily article:
Since the 1950s, scientists have known that the image of the Neanderthal as a hunched over caveman is not an accurate one. Their similarities to ourselves -- both in evolutionary and behavioral terms -- have also long been known, but in recent years the pendulum has swung in the opposite direction. "Focusing on the differences is back in fashion," says Martin Haeusler, UZH specialist in evolutionary medicine. For instance, recent studies have used a few isolated vertebrae to conclude that Neanderthals did not yet possess a well-developed double S-shaped spine.

However, a virtual reconstruction of the skeleton from La Chapelle-aux-Saints has now delivered evidence to the contrary. This computer-generated anatomical model was created by the research group led by Martin Haeusler from the University of Zurich and included Erik Trinkaus from Washington University in St. Louis. The researchers were able to show that both the individual in question as well as Neanderthals in general had a curved lumbar region and neck -- just like the humans of today.
This is the final nail in the coffin of the absolutely atrocious report that came out in 1913, written by Marcelin Boule1, in which he described the skeleton of the La Chapelle Neandertal as stooped over and primitive, doing his best to derail any possibility that Neandertals were related to modern humans.  Boule's work is an object lesson in how an, otherwise, respected scientist can let personal opinions completely cloud their scientific judgement. 

1Boule M (1911-13) L’homme fossile de La Chapelle-aux-Saints. Ann Paléontol 6:111–172, 7:21–56, 85–192, 8:1–70

Tuesday, February 05, 2019

Charles Darwin and the “Christian Right”

Interesting.  Nobody ever talks about the “anti-Christian left.” They are always referred to as “progressives” as though their ideas are brand new when, in fact, some of them date to the turn of the last century.  No matter.

Paul Rosenberg, of Salon, has a post that appears in Raw Story titled The brilliant science that has creationists and the Christian right terrified.  The story first ran in May of 2015 but I did not see it at the time.  To be fair, Rosenberg opens the piece with the following paragraph:
The Christian right’s obsessive hatred of Darwin is a wonder to behold, but it could someday be rivaled by the hatred of someone you’ve probably never even heard of. Darwin earned their hatred because he explained the evolution of life in a way that doesn’t require the hand of God. Darwin didn’t exclude God, of course, though many creationists seem incapable of grasping this point. But he didn’t require God, either, and that was enough to drive some people mad.
The problem I have here, of course, is that he doesn't define “Christian Right.” Reading between the lines, one might reasonably conclude he means Young Earth Creationists but, all the same, there should have been something here. Onward.  Having exonerated Darwin, however, he then makes an unwarranted leap beyond that initial paragraph. 
Darwin also didn’t have anything to say about how life got started in the first place — which still leaves a mighty big role for God to play, for those who are so inclined. But that could be about to change, and things could get a whole lot worse for creationists because of Jeremy England, a young MIT professor who’s proposed a theory, based in thermodynamics, showing that the emergence of life was not accidental, but necessary.
The bold is mine. He makes a point of separated YEC from OEC in the first paragraph and then conflates them in the second. Further, it is not clear in any sense why the “necessity” of life would obviate the need or existence of God.

The work of Jeremy England is key to this idea.  He has developed a mathematical formula to describe the fact that carbon atoms found in living organisms are better at harnessing external energy than inanimate groups.  As Rosenberg puts it, this puts the nail in the coffin of the idea that the second law of thermodynamics precludes evolution.  In fact, to use his phrase “thermodynamics drives evolution.”

The rebuttal to the claim that the second law of thermodynamics precludes evolution is pretty low-hanging fruit: the earth is obviously not a closed system.  It gets its energy from the sun.  Therefore, the idea that God is not active is not even addressed by the research.  Consequently, despite what Rosenberg writes, God may, indeed, be playing quite a large role.  This is yet another instance in which the existence of God cannot be tested one way or the other but the evidence makes the YEC position harder to maintain. 

Darwin Day Celebration in Knoxville

On Saturday, February 16, there will be a Darwin Day celebration at the Frank H. McClung Museum on the University of Tennessee Campus.  Here is the information.  The event will be from 1:00 to 4:00 and is open to the public.

Wednesday, January 30, 2019

New Florida Bill Would Advocate Teaching of Controversial Subjects

Emily Mahoney of the Tampa Bay Times writes that a new bill by senator Dennis Baxley (R, of course) has been promoted to allow teachers to teach alternatives to evolution and climate change.
A bill that would allow school districts to teach Florida students alternatives to concepts deemed “controversial theories” — such as human-caused climate change and evolution — has been filed in the state Legislature.

The language of the bill sounds fairly unremarkable, requiring only that schools “shall” teach these “theories” in a “factual, objective, and balanced manner.” But the group that wrote the bill, the Florida Citizens Alliance, says the bill is needed because curriculum currently taught in Florida schools equates to “political and religious indoctrination,” according to their managing director, Keith Flaugh.

The bill’s sponsor, Sen. Dennis Baxley, R-Ocala, said that schools need to teach “different worldviews” on issues like evolution and climate change. He asserts that textbooks now skew toward “uniformity” of thought.

“Nothing is ever settled if it’s science, because people are always questioning science,” Baxley said. “If you look at the history of human learning, for a long time the official worldview was that the world was flat. Anything you now accept as fact comes from a perspective and you learn from examining different schools of thought.”
First, a concession: I sympathize with the sponsors of the bill about the political and religious indoctrination. The Department of Education is lock-step with the DNC platform and, as such is hostile to “alternative” political views and religious expression. They tend to support every left, liberal cause that comes down the pike to the point where some teachers that I know won't be members of the national organization because they know that is where their membership money is being funneled.  This is one of very many reasons that we don't place our kids in public school. 

Secondly, though, this seems a whole lot like much ado about nothing.  While senator Baxley might want alternatives to established scientific theories taught, the text of the bill provides no language for that.  If anything, it gives teachers room to tee anti-evolutionary ideas up and knock them into the next fairway.  Climate change is a bit more sketchy.  It is a science in its infancy and, even fifteen years ago, researchers were warning of a coming big freeze (think The Day After Tomorrow, which came out in 2004).  Some still are.  There is a growing body of evidence that we are affecting the climate in some way, but it is still too early to tell how.  There is no value in cutting off debate in this arena.  The same cannot remotely be said about evolution, which now has over 150 years of supporting research behind it and is, in the minds of those who study it, almost beyond the realm of doubt. 

Tuesday, January 29, 2019

Mutation Rate in Humans Has Slowed Down

I am not quite sure what this means, yet. Researchers at the Aarhus University, Denmark, and the Copenhagen Zoo have discovered that, when compared to our nearest taxonomic relatives, our mutation rates have slowed down. Science Daily has the scoop:
"Over the past six years, several large studies have done this for humans, so we have extensive knowledge about the number of new mutations that occur in humans every year. Until now, however, there have not been any good estimates of mutation rates in our closest primate relatives," says Søren Besenbacher from Aarhus University.

The study has looked at ten families with father, mother and offspring: seven chimpanzee-families, two gorilla families and one orangutan family. In all the families, researchers found more mutations than would be expected on the basis of the number of mutations that would typically arise in human families with parents of similar age. This means that the annual mutation rate is now about one-third lower in humans than in apes.
Why is this important for the study of human origins?
The higher rates in apes have an impact on the length of time estimated to have passed since the common ancestor of humans and chimpanzees lived. This is because a higher mutation rate means that the number of genetic differences between humans and chimpanzees will accumulate over a shorter period.

If the new mutation rates for apes are applied, the researchers estimate that the species formation (speciation) that separated humans from chimpanzees took place around 6.6 million years ago. If the mutation rate for humans is applied, speciation should have been around 10 million years ago.
The six-to-eight million year point for the LCA never made a whole lot of sense to me. If the fossil material from Orrorin, at 6 mya really does reflect bipedality, then the split has to have been much earlier.  The material from Ardipithecus kadabba is very sketchy with regard to bipedalism (one toe bone found ten miles away), but the fragmentary post-cranial bones can be confidently identified as being hominin, in nature.  Furthermore, the fossil material is dated to between 5.6 and 5.8 mya.  That would leave a very short period of time.  It cannot be pre-split because the fossil material exhibits derivations in the hominin direction, rather than the modern ape direction. 

If this study holds up, it will change how we view the search for the LCA. 

Tuesday, January 22, 2019

My Favorite Fossil Post Up on BioLogos

Unbeknownst to me, my “My Favorite Fossil” post on BioLogos is up.  You can view it here.  Comments welcome in both places. 

Friday, January 18, 2019

'Swiss Army knife of prehistoric tools' Found in China

Science Daily is on a roll.  This came out a bit back during the late semester crunch and I didn't get a chance to post about it.  Stone tools have been found in south China that appear to be made using the Levallois technology, which originated during the Middle Stone Age, in Africa.  They write:
A study by an international team of researchers, including from the University of Washington, determines that carved stone tools, also known as Levallois cores, were used in Asia 80,000 to 170,000 years ago. Developed in Africa and Western Europe as far back as 300,000 years ago, the cores are a sign of more-advanced toolmaking -- the "multi-tool" of the prehistoric world -- but, until now, were not believed to have emerged in East Asia until 30,000 to 40,000 years ago.
And now the, somewhat, startling conclusion:
With the find -- and absent human fossils linking the tools to migrating populations -- researchers believe people in Asia developed the technology independently, evidence of similar sets of skills evolving throughout different parts of the ancient world.
This particular conclusion seems somewhat ignorant of the fossil record, which clearly has hominins in the area that have distinct Neandertal traits.  The authors, in fact, even mention the possibility that the appearance of the tools might be tied to these earlier migrations, then seem to dismiss this for reasons that are, in my mind, not clear. 

The site, itself, Guanyindong Cave in Guizhou Province, is not new, having been excavated in the 1960s and 1970s.What is new is the date of 80-170 kya.  Levallois tools were thought to have arrived in the area around 30-40 kya and are seen as the artifacts of a late migration.  This re-dating of the sediments of Guanyindong Cave means that these kinds of tools were in the area some 100 ky earlier than was originally thought.  I do, however, think their evidence for independent origin is sparse. 

Thursday, January 17, 2019

New Data on Neandertal Anatomy

Anatomists have reconstructed the rib cage of the Kebara 2 Neandertal to get a better understanding of the trunk of our nearest relatives.  Science Daily has the story:
An international team of scientists has completed the first 3D virtual reconstruction of the ribcage of the most complete Neanderthal skeleton unearthed to date, potentially shedding new light on how this ancient human moved and breathed.

The team, which included researchers from universities in Spain, Israel, and the United States, including the University of Washington, focused on the thorax -- the area of the body containing the rib cage and upper spine, which forms a cavity to house the heart and lungs.
What did they find?
The reconstruction of the thorax, coupled with the team's earlier finding, shows ribs that connect to the spine in an inward direction, forcing the chest cavity outward and allowing the spine to tilt slightly back, with little of the lumbar curve that is part of the modern human skeletal structure. "The differences between a Neanderthal and modern human thorax are striking," said Markus Bastir, senior research scientist at the Laboratory of Virtual Anthropology at the National Museum of Natural History in Spain.

"The Neanderthal spine is located more inside the thorax, which provides more stability," said Gomez-Olivencia. "Also, the thorax is wider in its lower part." This shape of the rib cage suggests a larger diaphragm and thus, greater lung capacity.
In my anthropology class, I teach about the effects of Bergmann's and Allen's rules of body morphology. In the case of Neandertals, the adaptations to the cold were shortened distal limb segments, a large, projecting mid-face and a tendency toward barrel-chestedness. The new study reinforces these ideas.

Interestingly, it should be noted that the Kebara Neandertal is found in Israel, not known for its cold climate.  It is hypothesized that the Neandertal population came down from Eastern Europe to escape the cold (the tundra line was at Vienna).  What is peculiar about the Kebara 2 Neandertal is that it consists only of a body.  Whether he died and his head fell in a stream or some animal carried it off, there is no cranium.  Oddly, what we do have is one of the bones that is preserved least in the fossil record: a hyoid.  It is this that has given us the most information about the Neandertal vocal tract.

Fun stuff.