Thursday, January 09, 2020

EarthSky: Twenty years of discoveries changing story of human evolution

EarthSky has an interesting article that summarizes twenty years of human evolution discoveries.  They write:
Perspectives on our own species have also changed. Archaeologists previously thought Homo sapiens evolved in Africa around 200,000 years ago, but the story has become more complicated. Fossils discovered in Morocco have pushed that date back to 300,000 years ago, consistent with ancient DNA evidence. This raises doubts that our species emerged in any single place.
This century has also brought unexpected discoveries from Europe and Asia. From enigmatic “hobbits” on the Indonesian island of Flores to the Denisovans in Siberia, our ancestors may have encountered a variety of other hominins when they spread out of Africa. Just this year, researchers reported a new species from the Philippines.
All of these discoveries point to the idea that there was considerable population mixing throughout the Middle to Late Pleistocene not just in Africa but throughout the Old World. We know that it took place in China around 120,000 years ago by the evidence from Linjing.  These particular hominins have characteristics found in modern humans, Neandertals and Homo erectus.

Interestingly, the idea that our species did not originate in any single place was an idea pursued by Rachel Caspari almost two decades ago, at a paper given at one of the American Association of Physical Anthropologists conventions.  At the time, it was still thought that the “Out of Africa” replacement model was still the best explanation for modern human origins.We now know that it is not.

Wednesday, January 08, 2020

New Spot for the Origins of Modern Humans: Botswana

One thing is consistent in the study of the origins of modern humans: there isn't any.  What National Geographic calls a “controversial” new study pinpoints the origins of our line in Botswana:
A powdery white layer blankets the desiccated landscape of Botswana’s Makgadikgadi pans, one of the world's largest salt flats. But some 200,000 years ago, this blank canvas would have been painted in the blues and greens of a flourishing wetland. Set in the middle of a harsh desert in southern Africa, the lush landscape would have been an appealing place for early humans to call home.

Now, a controversial new study in Nature argues that this oasis, known as the Makgadikgadi–Okavango wetland, was not just any home, but the ancestral “homeland” for all modern humans today. The researchers studied mitochondrial DNA—genetic material stored in the powerhouse of our cells that is passed from mother to child—of current residents across southern Africa. Then they layered the genetic data with an analysis of past climate and modern linguistics, as well as cultural and geographic distributions of local populations.
We've seen this play before.  The Nature article is an odd one.  It purports to examine the origins of modern humans using mitochondrial DNA evidence but then goes out of its way to not mention ANY of the fossil evidence that does not fit the hypothesis constructed in the paper.  How did the editors of Nature let that get by?  There is no mention of either the East African Bouri or the Northwest African Jebel Irhoud sites in this paper.  The Bouri site contains the Herto remains that are demonstrably modern human at 160 thousand and the Jebel Irhoud remains, which date to around 315 thousand exhibit modern facial characteristics.  The 180 thousand year-old East African Omo remains are only mentioned in passing and then, not by name. 

Friday, November 15, 2019

Todd Wood's Take on Danuvius

Todd Wood is always interesting to read, even if I don't share his chronological leanings.  He has thoughts on the new Miocene ape from Bavaria, Danuvius:
Based on the fragmentary remains, we make some really interesting observations about the anatomy of Danuvius. These apes had strongly opposed big toes, which would allow them to effectively grip things with their feet. Their tibiae (shinbones) have the kinds of joints that would allow them to walk upright, and their femora (thighbones) support that conclusion. These apes might have been in some way bipedal. The arm bones they found have traits that are associated with suspensory locomotion, like hanging from tree branches. The body size was fairly small, about the mass of a bonobo.
As I mentioned in my post, I think the evidence for bipedalism is vastly over-stated and, even if it can be shown that this “Extended Limb Clambering” is shared by other fossil ape finds from the region, there is no particular reason to think that these critters were ancestral to later hominins. It is entirely likely that they exhibited a separate adaptation to this particular style of locomotion.  Todd raises some other questions, though, that are not answered in the paper:
So why not address similarities of Danuvius to later fossil hominins? The authors are trying to establish a new means of locomotion that they call Extended Limb Clambering (ELC). So they compare Danuvius to living primates (where the authors know how they get around), and they're interested in comparing it to contemporary Miocene apes of Europe. But they're not all that excited about other comparisons to later fossil forms like Ardipithecus, Australopithecus, or Orrorin. They also don't relate their findings to later fossil apes in Europe like Graecopithecus or the Trachilos tracks, both of which have been linked to hominins or bipedality. Perhaps they don't think those things are worth talking about (maybe because they're skeptical of Graecopithecus like I am), but I guess I just don't agree.
I think that part of the reason that these questions are not raised is because there is so much of a gap between these finds, chronologically and geographically. There is simply with which to relate them. As Todd points out, the hominin status of Graecopithecus is dubious, at best, and, even if the Trachilos tracks are hominin, they are still quite a distance from Bavaria and six million years later in time.

For now, this fossil ape stands on its own.  If we find other evidence of incipient bipedality in other forms in the area and can relate them to later forms, then the picture might change.  For now, though, Danuvius is a very interesting, odd Miocene ape. 

Thursday, November 14, 2019

Upright Ape?

Multiple outlets are reporting on the discovery of a fossil ape that appears to have at least a partially facultatively bipedal stance.  Here is the Fox News version of events:
The remains of an 11 million-year-old ape suggest that our ancestors started to stand upright millions of years earlier, according to scientists.

A team of researchers claims the fossilized partial skeleton of a male ape that lived in the humid forests of what is now southern Germany bears a striking resemblance to modern human bones. In a paper published on Wednesday by the journal Nature, they concluded that the new species — dubbed Danuvius guggenmosi — could walk on two legs but also climb like an ape.

The findings “raise fundamental questions about our previous understanding of the evolution of the great apes and humans,” Madelaine Boehme of the University of Tuebingen, Germany, who led the research, told The Associated Press.
Here is how the Nature paper actually reads:
Here we describe the fossil ape Danuvius guggenmosi (from the Allgäu region of Bavaria) for which complete limb bones are preserved, which provides evidence of a newly identified form of positional behaviour—extended limb clambering. The 11.62-millionyear-old Danuvius is a great ape that is dentally most similar to Dryopithecus and other European late Miocene apes. With a broad thorax, long lumbar spine and extended hips and knees, as in bipeds, and elongated and fully extended forelimbs, as in all apes (hominoids), Danuvius combines the adaptations of bipeds and suspensory apes, and provides a model for the common ancestor of great apes and humans.
First, this is way-the-heck back there, some five and a half million years before the first actual evidence of bipedalism (Orrorin). Second, there are no “hip” remains. The only post-cranial remains are long bones.  Much is inferred.  In hominins, the femoral neck and the connection to the femoral head provide much diagnostic locomotion information.  The fossil remains for this region are very scant, consisting only of a partial head.  Much of the argument for even some bipedality rests with the tibial angle, to wit:
The near perpendicular tibial angle is a shared character between hominins and Danuvius and supports the inference of a habitual valgus knee position and bipedalism for the new genus.
I think a new genus designation is certainly warranted. I have grave reservations about the “bipedalism” designation. We have possible evidence from Crete at 5.5 million years for bipedalism in the form of footprints. That is as far north as it gets.  All of the other evidence we have for the emergence of hominins and bipedalism comes from North Africa.  It is far more likely that this represents an independent adaptation/homoplasy for this hominoid.   If we had more evidence from later in the Miocene or, better yet, the Pliocene, then this might carry more weight.

Tuesday, September 24, 2019

Denisovans More Closely Related to Modern Humans than Neandertals

Science Daily has a post relating recent research on the genetic studies involving the Denisovan material from Siberia.  The research, done by CNRS in France has this to report:
Now a team of scientists from the Institut Jacques Monod (CNRS / Université de Paris) has measured and photographed another fragment found in Denisova Cave. Genomic analysis reveals it is the missing piece of the same phalanx whose proximal fragment enabled initial sequencing of the Denisovan genome.

Together with colleagues from the PACEA laboratory (CNRS / University of Bordeaux / French Ministry of Culture) and the University of Toronto (Canada), the scientists compared the new fragment to the phalanges of Neanderthals and anatomically modern humans. Their analysis indicates it is very close to the latter, and less like the former..
This research suggests that there was considerable population mixing and genetic variability in this population, given the news that came out last year detailing the finding of a child skeleton that was, as nearly as the researchers could tell, the offspring of a Neandertal and a modern human.This just continues to solidify the idea that these groups interbred routinely throughout the late Pleistocene. 

Wednesday, August 21, 2019

More Information About the Denisovans

Discover Magazine has an article on new finds at Denisova and their context in early modern human evolution.  Bridget Alex writes:
Nestled in foothills of Russia’s Altai Mountains, Denisova Cave has been a research mecca since 2010, when fossil DNA from the site revealed a previously unknown human lineage, now called the Denisovans. Scientists have been working hard to reconstruct the cave’s history, through ongoing excavations as well as new analyses of materials recovered years ago.

First, what everyone wants to know: Yes, they found more human remains. In addition to the four Denisovan specimens (one pinky finger, two adult molars and a baby tooth), the cave has yielded 12 fossils from ancient humans, including teeth, toes, fingers and unclassifiable fragments.

Based on their genomes, proteins and physical appearance, the collection contains four Denisovans, three Neanderthals and one hybrid cross between the two human types. Excavators have also found four more fossils that belong to the Homo genus, but haven’t yet been assigned to a particular human species. Additional DNA sequences, recovered directly from the dirt, suggest the presence of even more individuals.
As reported last year, Denisova 11 has been determined to be the offspring between a Neandertal mother and Denisovan father. As with other finds in Asia, we are finding that there appears to have been considerable population mixing over the course of at least 100 thousand years. Although the article indicates that the Neandertals were “sandwiched” in between two modern human occupations, that is difficult to square with any hybridization model. I suspect that the habitation patterns were more complex.

Wednesday, August 07, 2019

Space X Launch Fails After Rocket Bounces Off Firmament

I think I worried my family last night by laughing so hard at this story that they thought I was going to herniate.  Those of you who follow the news know that Babylon Bee is in a tussle with Snopes about whether or not their stories constitute “fake news.”  Anyone with two grey cells to rub together knows the difference, including Snopes, but they are trying to get the Bee de-platformed because quite a few of the Bee's stories point out the idiocy of some of their favorite political positions.

Anyway, the Bee is not above poking fun at just about anything in the Christian world and I missed this story when it came out.
A SpaceX launch ended in tragedy Thursday as the rocket intended to carry a cellular satellite into orbit around the earth bounced off the firmament described in the opening chapters of Genesis, sources confirmed.

The rocket accelerated higher and higher above the flat earth and toward the sun and moon a mere 3,000 miles away before suddenly bouncing off the glass-like dome containing the earth.

“We totally didn’t see this coming,” a SpaceX launch expert told reporters moments after the crash. “Where we seem to have gone wrong is in using NASA’s fake globe model rather than employing flat-earth models drawn by conspiracy theorists operating off ultra-literalist readings of the King James Bible.”

“We won’t make that mistake again, I tell you what,” he added.
They manage to skewer the literal reading of Genesis and the biblical evidence for a flat earth in one post.  Many Christian writers, including Phil Senter and John Walton, have written about the language describing the firmament and have argued (persuasively, in my opinion) that it can only be read as a hard dome because that is how the ANE people saw it. 

Humor at its best.

Friday, August 02, 2019

Lutheran Church Tackles Creation Days

Christian Post has an article on the recent Lutheran Synod resolution involving the “creation days.” Michael Gryboski writes:
The Lutheran Church—Missouri Synod passed a resolution at their convention affirming the belief that God created the Earth “in six natural days.”

At the 67th Regular Convention of The Lutheran Church—Missouri Synod on Tuesday, the theologically conservative denomination adopted Resolution 5-09A, titled “To Confess the Biblical Six-Day Creation.”

“We confess that the duration of those natural days is proclaimed in God’s Word: ‘there was evening and there was morning, the first day,’” resolved the resolution.

The resolution also declared that the creation of Adam as the first human being was a “historical event” and rejected the claims of the theory of evolution.
As noted in the article, there is some debate about what the word “natural” means in this context.
Another delegate expressed concern over the alleged “lack of clarity” on the definition of the word “natural” as used in the resolution.

Supporters responded that the term “natural” was defined by the Bible’s own words, describing the days as having an evening and a morning.
This has always struck me as a peculiar defense given how the scriptures actually reads:
14 And God said, “Let there be lights in the vault of the sky to separate the day from the night, and let them serve as signs to mark sacred times, and days and years, 15 and let them be lights in the vault of the sky to give light on the earth.” And it was so. 16 God made two great lights—the greater light to govern the day and the lesser light to govern the night. He also made the stars. 17 God set them in the vault of the sky to give light on the earth, 18 to govern the day and the night, and to separate light from darkness. And God saw that it was good. 19 And there was evening, and there was morning—the fourth day. (Genesis 1:14-19, NIV)
Every translation reads pretty much the same way.  That happens on the fourth day. Without the sun and moon, you cannot have “evening and morning.”  There is no reasonable context for it.  To argue this implies that the entire universe revolves around a 24-hour earth day.  We know this is not so.

It is notable that the vote was 662 in favor and 309 against, so there is quite a bit of dissent about the resolution.  The rider involving evolution, while not taking center stage, is a slap in the face to those congregants who accept it.  The rising science of coalescence theory is hard to square with the idea of Adam and Eve being the first humans.   As Dennis Venema and Scot McKnight put it in their book Adam and the Genome,
As our methodology becomes more sophisticated and more data are examined, we will likely further refine our estimates in the future. That said, we can be confident that finding evidence that we were created independently of other animals or that we descend from only two people just isn’t going to happen. Some ideas in science are so well supported that it is highly unlikely new evidence will substantially modify them, and these are among them: The sun is at the center of our solar system, humans evolved, and we evolved as a population.
I always find it somewhat interesting that these large denominations fight tooth-and-nail over social issues that are somewhat fluid in society, such as homosexuality and female ordination, and yet, for issues in which there is actually hard, scientific evidence, retreat to a very flat, conservative interpretation of scripture.

Interestingly, the new T-shirt being issued by the Evangelical Lutheran Church of America celebrates both science and LGBT rights.  That is not true for the science part.

Sunday, July 28, 2019

New Poll From Gallup on Human Origins

Gallup has released a new poll on what people think about human evolution.  Here is their takeaway blurb:
Forty percent of U.S. adults ascribe to a strictly creationist view of human origins, believing that God created them in their present form within roughly the past 10,000 years. However, more Americans continue to think that humans evolved over millions of years -- either with God's guidance (33%) or, increasingly, without God's involvement at all (22%).
Beyond this are details in the numbers.The poll was conducted from June 3-16 and contained a random sample of 1015 adults.  Some of this is not new and has changed little since the last poll.  There is a high correlation between those with a college education and those who accept human evolution.  The correlation is also high between those who have no religious affiliation and those who accept human evolution.

Other interesting tidbits from the attached PDF:
  • Acceptance of God-guided human evolution does not seem to change with political party affiliation, gender or ethnic background
  •  Acceptance of God-guided human evolution rises only slightly with age
  • The idea that God created humans in their present form drops substantially from 55% (Republican) to 34% (independent and Democrat) as well as ideology (54% Republican, 29% democrat)
There are more observations buried in the data. Have a look.

Saturday, July 27, 2019

Chris Stringer: Meet the Relatives

Chris Stringer has a post in the Financial Times titled Meet the Relatives.  It is sort of a whirlwind tour through the evolution of the genus Homo.    He writes:
The discoveries of Homo floresiensis, Homo luzonensis, Denisovans and Homo naledi in the past 15 years remind us that the fossil record of humans is still very patchy — stone tools are scattered across much of Africa as a witness to widespread human occupation, yet fossil evidence has been recovered from less than 10 per cent of that continent’s area.

The percentage coverage for Asia is hardly any better: there is, for example, currently only one significant human fossil from the whole of the Indian subcontinent. The discoveries of the past few years underline just how much evolutionary history remains unknown, with other extinct lineages no doubt still to be revealed.

Many of the new finds challenge how we classify fossils in relation to Homo sapiens today. I continue to call the Neanderthals a different species from us, based on their distinctive skeletons and skulls; others feel that the recent evidence of interbreeding and increasing evidence of sophisticated behaviour mean that we should merge them, and the Denisovans, into our species.
I think that the discovery of the Xuchang hominins indicates that there has been considerable population mixing for several hundred thousand years.  As I wrote at the time:
These two Chinese skulls stand at the crossroads of these population movements. While showing clear Neandertal characteristics, they also express modern traits, possibly reflecting mixing with the late, modern human arrivals represented by the recent modern human finds at Daoxian. Yet they also express a clear link to ancient East Asian populations. The implications of these skulls are stark: there has been widespread population mixing and regional continuity in Europe and Asia for at least 400 thousand years. Not only did the Neandertals feel enough cultural kinship to mate and have children with these East Asian people, the early modern humans coming out of Africa did, as well. As Chris Davis of China Daily News put it: “One big happy family.”
Whether this represents such behavior at the peripheries of different species or that of one polytypic species is, as yet, unclear.  It is very clear that our understanding of how these populations interacted is rudimentary, at best.