Friday, 18 January 2019

Lagoa Santa skulls still perplex Danes

Peter Wilhelm Lund (1801-1880)
Danish National Library (public domain)
When Peter Lund excavated human remains from Sumidouro Cave he was thoroughly perplexed. Not least because they were jumbled together with the bones of an extinct megafauna. This was in 1840 so well before Darwin had published On the Origin of Species (which cites Lund's work).

The skeletons were shipped to Copenhagen and examined there by several distinguished anthropologists (Lund never returned to Denmark). The consensus that arose was that "Lagoa Santa Man" was unrelated to present-day Native Americans. 


Springer 2017: ISBN 978-3-319-57465-3
Research and debate was renewed in the last century with new excavations in the caves near Lagoa Santa (now a suburb of Belo Horisonte). A key find was Luzia, a skull feared lost in the recent fire at the National Museum in Rio de Janeiro (previous post) (it survived but suffered heat damage). This skull was dated to 11,000 years ago.

Comparisons have been drawn between the features of the Lagoa Santa skulls and those of Australasian peoples such as Andaman Islanders. What can genomics tell us? A first set of clues hinted at an early wave of migrants designated "Population Y" who left a genetic signature that is strongest in some isolated Brazilian communities (see my review of David Reich)


Skull from Sumidouro Cave excavated by Peter Lund
Now a Dane has ventured into the Lund Collection and extracted ancient DNA from a 10,400 year-old skull. The results appeared in Science last December (here). Eske Willeslev and his group found a clear Australasian genomic signature that was absent in other ancient remains from the Americas. They concluded this signal, "implies that an early group possessing it had disappeared or that a later-arriving group passed through North America without leaving any genetic trace." A conclusion echoed by the lead author, José Victor Moreno-Mayar, who simply said (here), "How did it get there? We have no idea."

It seems the Lagoa Santa remains are just as perplexing to Willerslev as they were to Lund and for a similar reason: they do not neatly fit into the scheme of things.

Postscript

The Willerslev paper is really worth reading. It builds on earlier work to confirm that Native Americans (other than Inuits) derived from a group that split from East Asians and resided in Beringia (Ancient Beringians). As they advanced into the Americas at the end of the Ice Age there was an early split into Northern (NNA) and Southern Native Americans (SNA). The SNA dispersed rapidly south of the remaining ice some 14,000 years ago. In a later phase there was admixture from a population in Mesoamerica that migrated both north and south. Another paper on ancient DNA from the Reich group also found evidence for rapid expansion into South America (here), but did not have Lagoa Santa in the data set.

Monday, 14 January 2019

Darwin's hunch

ISBN 978-1-4314-2425-2
Darwin's hunch was that humans evolved in Africa. As Christa Kuljian shows, for most of the twentieth century, this was not the prevailing view among palaeoanthropologists, who felt sure humans had emerged in Europe or Asia. Indeed, the ready acceptance of the Piltdown forgery reflected both this view and the importance attached to brain size. In contrast, the Taung child, an australopithecine discovered in 1924 by Raymond Dart, was disregarded because of its location and small brain size. 


The Taung child (Australopithecus africanus) discovered in 1924
Ditsong National Museum of Natural History CC BY-SA 4.0
Indeed this highly entertaining account of the South African contribution to anthropology by Dart, Robert Broom, Phillip Tobias and others exposes how misconceptions both within South Africa and without shaped interpretation of the fossil record.

Many of the same scientists were involved in biometric studies of living people. These were troublesome because of implicit racial bias. Support for such studies was forthcoming from Jan Smuts and other politicians with a racial agenda. Particularly disturbing was the treatment afforded to the "bushmen" or San people. Anthropologists such as Tobias and Hertha De Villiers were much interested in such female characteristics as steatopygia (increased fat in the region of the buttocks) and elongated labia minora. 

This book was published over a year ago and I was alerted to it by a lengthy review (and opinion piece) by Rebecca Rogers Ackermann (here). It certainly provides food for thought.

The book also covers more recent conflicts between South African palaeoanthropologists such as Ron Clarke and Lee Berger. This has again come to the fore with publication by Clarke of the first description of the australopithecine known as Little Foot (e.g. here) and the hasty reaction from Berger (here). 

The book does not go into detail about phylogenomics and studies of ancient and modern DNA. These provide robust support for the Recent African Origin hypothesis of human origins argued since 1988 by Chris Stringer (here). And thus for Darwin's hunch. Genomics is set to cast new light on the history of the San as recently reported in Nature (here).




Wednesday, 31 October 2018

Placenta Atlas Tool (PAT)

NICHD have just launched this tool to aid pregnancy research. It promises to be of great value (found here).

Those interested in comparative placentation should go to Explore Images and use the Species filter. This brings up a list that may include your favourite mammal. Click on that and you will get a menu of large icons, although only after a further click can you be sure what they represent (room for improvement here).

The images are fully annotated with original figure legends plus additional context from the source paper.

Open Access appears to be a prerequisite for images to be selected as they link to the Open-i resource of the U. S. National Library of Medicine. 

Monday, 22 October 2018

Pregnant tenrecs run hot and cold

Tailless tenrec (Tenrec ecaudatus)
Photo by Markus Fink (Wikimedia Commons CC)
Tenrecs do not maintain a constant body temperature. It waxes and wanes throughout the day. A recent study found this applies even to pregnant tenrecs. Yet after they give birth their body temperature becomes stable and warm.

As mentioned in a recent post, this tenrec (Tenrec ecaudatushas large litters. In the present study up to 19 young. They grow quickly from 12 g at birth to 400 g at 5 weeks (weaning). Perhaps thermoregulation becomes more important when the mother is lactating.

In the closely related species Echinops telfairi, gestation length varies in the range 50-79 days (here). Just speculating, but if body temperature varies could this affect fetal growth rate and thereby the timing of delivery?

Reproduction in tenrecs is quite interesting as we discuss for the ovary here and placenta here.

Monday, 8 October 2018

Congratulations Hiroaki Soma

Professor Hiroaki Soma (at left) recipient of the 2018
IFPA Senior Award
It is a pleasure to record that my good friend and colleague Hiroaki Soma received the Senior Award of the International Federation of Placenta Associations at their recent meeting in Tokyo.

In his address, Professor Soma looked back over 60 years of research including important clinical work on gestational trophoblastic disease in Japan and placental lesions associated with pregnancy at high altitude in Nepal.

In addition, he gave valuable insights about comparative placentation. The range of mammals included chinchilla, giant panda. Japanese serow, sloth, chimpanzee, elephant, manatee and hyrax. As if this were not enough, Professor Soma also presented his research on pregnancy in sharks and rays conducted at the Churaumi Aquarium in Okinawa. 

Friday, 14 September 2018

Kurt Benirschke (1924 - 2018)

Kurt Benirschke (right) with Oliver Ryder
Sad to record the death of Kurt Benirschke at age 94. Among many achievements is his web site Comparative Placentation (previous post). This invaluable resource is particularly strong on primates and even-toed ungulates such as antelopes.

The placentas came mainly from San Diego Zoo where Kurt Benirschke also took the initiative to create a biobank of cryopreserved tissues (The Frozen Zoo) and laid the foundation for what became San Diego Global's Institute for Conservation Research. 

To many he is best known for his textbook Placental Pathology. The second  (1990) and subsequent editions were written with Peter Kaufmann. It is now in a sixth edition edited by Kurt Benirschke, Graham Burton and Rebecca Baergen.


The Annual Kurt Benirschke Lecture at UC San Diego 2018
Five years ago Kurt Benirschke suffered a stroke but he remained active and alert. According to today's obituary in San Diego Union Tribune, he and his wife visited San Diego Zoo as recently as last week. 

To learn about Kurt Benirschke's life in his own words see the short version here or his interview with Rebecca Baergen here.

Wednesday, 5 September 2018

Why Luzia was important

Cast of the skull known as Luzia as displayed at
National Museum of Natural History Washington DC
Photo by Ryan Somma CC BY-SA 2.0
Luzia was excavated from Lapa Vermelha, Minas Gerais, Brazil and was the oldest human fossil from South America. She was found in strata dated to 11,000 years ago. Whilst casts of the skull exist elsewhere the original was lost (at best severely damaged) in the catastrophic fire that destroyed the National Museum in Rio de Janeiro. 

Luzia Woman belonged to an ancient population formerly known as Lagõa Santa Man or Paleoamerind. The first to excavate such skulls was the Danish Naturalist Peter Lund, who found them as far back as 1840. Based on the classical craniometric criteria used by anthropologists until well into the twentieth century, this population clearly diverged from all others in North and South America.

Lagõa Santa skull excavated 1840 by Peter Wilhelm Lund
There is an interesting correlate in modern genomic data. David Reich and colleagues postulate an ancient Population Y corresponding to a genetic signal borne by the Surui people of the Amazon region (discussed here - see previous post for Reich's book where this is further discussed). The interesting thing about this signal is that it is shared with the faraway Andaman Islanders and natives of New Guinea and Australia.

We already know of two branches to the population that crossed the Bering Strait and peopled North and South America - thanks to work by Eske Willerslev's group (here). Was there a third branch that gave rise to the Paleoamerinds or even a separate and earlier migration?

To piece this together it would have been useful to extract ancient DNA from the Luzia skull. That had not been done prior to the fire. There are other skulls around including those excavated by Peter Lund and now housed in Copenhagen. They may yet yield new pieces to complete the puzzle.