Friday, 30 April 2021

The Ever-Shrinking God of the Gaps Just Got a Bit Smaller.

This skull of the extinct horned crocodile from Madagascar (Voay robustus) has been part of the American Museum of Natural History’s scientific collections since the early 1930s.

Credit: M. Ellison/© AMNH
Ancient DNA of Crocodile Sheds Light on Croc Family Tree | AMNH

It has been said the creationism's God of the Gaps is the only thing faster than light because it's always gone just before Science shines its light in the gap, leaving Creationists to search around for another gap to put it in - or invent one if they can't find one.

Just such a gap was found to be empty a few days ago when science solved an ongoing puzzle - how did the extinct Madagascan horned crocodile fit in the crocodile family tree? It was quite obvious from just looking at it that it was a crocodile of some sort but its evolutionary relationship to the others was unknown - until now. The key to closing the gap was the recent advance in the recovery and analysis of ancient DNA - the same scientific advance that is proving the Theory of Evolution to be correct, closing gaps and evicting gods by the dozen.

The Madagascan horned crocodile, Voay robustus (artist's impression)

In this case, it turned out that the Madagascan horned crocodile, Voay robustus, was very much part of the crocodile family tree but deserved a branch in the tree all to itself.

A research report from the American Museum of Natural History tells the story:
New research based on two skulls that have been in the Museum’s collection since the early 1930s resolves a long-standing controversy about an extinct “horned” crocodile that lived in Madagascar.

This crocodile was hiding out on the island of Madagascar during the time when people were building the pyramids and was probably still there when pirates were getting stranded on the island. They blinked out just before we had the modern genomic tools available to make sense of the relationships of living things. And yet, they were the key to understanding the story of all the crocodiles alive today.

Teasing apart the relationships of modern crocodiles is really difficult because of the physical similarities. Many people don’t even realize that there are multiple species of crocodiles, and they see them as this animal that’s unchanging through time. But we’ve been trying to get to the bottom of the great diversity that exists among them.

Evon Hekkala, Lead author
Associate professor, Department of Biological Sciences
Fordham University,
Bronx, NY, USA
(Research associate at the American Museum of Natural History)
The research team found that the horned crocodile, Voay robustus, known for the two bony knobs at the top of its head, was closely related to “true crocodiles,” but on a separate branch of the crocodile family tree.

“This crocodile was hiding out on the island of Madagascar during the time when people were building the pyramids and was probably still there when pirates were getting stranded on the island,” said Evon Hekkala, an associate professor at Fordham University and a research associate at the Museum who is the lead author of the study, which is published today [April 26, 2021] in the journal Communications Biology. “They blinked out just before we had the modern genomic tools available to make sense of the relationships of living things. And yet, they were the key to understanding the story of all the crocodiles alive today.”

Early explorers to Madagascar noted that Malagasy peoples consistently referred to two types of crocodiles on the island: a large robust crocodile and a more gracile form with a preference for rivers, suggesting that both types existed until very recently. But only the gracile form, now recognized as an isolated population of the Nile crocodile, Crocodylus niloticus, is currently found on the island.

Despite nearly 150 years of investigation, the position of the horned crocodile in the tree of life has remained controversial. In the 1870s, it was first described as a new species within the “true crocodile” group, which includes the Nile, Asian, and American crocodiles.

In the early part of the 20th century, it was thought that the specimens simply represented very old Nile crocodiles. Then, in 2007, a study based on physical characteristics of the fossil specimens concluded that the horned crocodile was actually not a true crocodile, but in the group that includes dwarf crocodiles.

“Teasing apart the relationships of modern crocodiles is really difficult because of the physical similarities,” Hekkala said. “Many people don’t even realize that there are multiple species of crocodiles, and they see them as this animal that’s unchanging through time. But we’ve been trying to get to the bottom of the great diversity that exists among them.”

This is a project we’ve tried to do on and off for many years, but the technology just hadn’t advanced enough, so it always failed. But in time, we had both the computational setup and the paleogenomic protocols that could actually fish out this DNA from the fossil and finally find a home for this species.

This finding was surprising and also very informative to how we think about the origin of the true crocodiles found around the tropics today. The placement of this individual suggests that true crocodiles originated in Africa and from there, some went to Asia and some went to the Caribbean and the New World. We really needed the DNA to get the correct answer to this question.

George Amato, Co-author
Emeritus director of the Institute for Comparative Genomics,
American Museum of Natural History.
To investigate the horned crocodile’s place in the evolutionary tree, Hekkala and her collaborators at the Museum made a number of attempts to sequence DNA from fossil specimens, including two well-preserved skulls that were collected during the Museum’s Mission Franco-Anglo-American expedition from 1927–1930.

“This is a project we’ve tried to do on and off for many years, but the technology just hadn’t advanced enough, so it always failed,” said study co-author George Amato, emeritus director of the Museum’s Institute for Comparative Genomics. “But in time, we had both the computational setup and the paleogenomic protocols that could actually fish out this DNA from the fossil and finally find a home for this species.”

The results place the horned crocodile right next to the true crocodile branch of the evolutionary tree, making it the closest species to the common ancestor of the crocodiles alive today.

“This finding was surprising and also very informative to how we think about the origin of the true crocodiles found around the tropics today,” Amato said. “The placement of this individual suggests that true crocodiles originated in Africa and from there, some went to Asia and some went to the Caribbean and the New World. We really needed the DNA to get the correct answer to this question.”
The research team published their findings a few days ago, open access in Communications Biology:

Abstract


Ancient DNA is transforming our ability to reconstruct historical patterns and mechanisms shaping modern diversity and distributions. In particular, molecular data from extinct Holocene island faunas have revealed surprising biogeographic scenarios. Here, we recovered partial mitochondrial (mt) genomes for 1300–1400 year old specimens (n = 2) of the extinct “horned” crocodile, Voay robustus, collected from Holocene deposits in southwestern Madagascar. Phylogenetic analyses of partial mt genomes and tip-dated timetrees based on molecular, fossil, and stratigraphic data favor a sister group relationship between Voay and Crocodylus (true crocodiles). These well supported trees conflict with recent morphological systematic work that has consistently placed Voay within Osteolaeminae (dwarf crocodiles and kin) and provide evidence for likely homoplasy in crocodylian cranial anatomy and snout shape. The close relationship between Voay and Crocodylus lends additional context for understanding the biogeographic origins of these genera and refines competing hypotheses for the recent extinction of Voay from Madagascar.

Once again, when a gap was closed by science, no evidence of gods, magic or special creation fully formed as is, was found. In fact, what evidence was found was entirely consistent with the Theory of Evolution and the idea that all life forms share a common origin and are the result of diversification by an entirely natural process. As usual, no need and no room for gods in the explanation and Creationism's ever-shrinking little god just got a bit smaller.


Thank you for sharing!









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