New research related to the famous 47-million-year-old fossil Ida cuts open controversy on more than one level. It also offers some sobering lessons for science popularizers.
Remember Ida aka Darwinius masillae? The fossil won instant fame after her debut in May this year. She was featured in a History Channel special and a book, given her own website and even given a temporary starring role as the double O in Google’s logo.
Ida was touted as the “missing link” in the evolution of humans and other higher primates. One television report suggested we humans think of her as our very early aunt.
From the get-go, though, evolutionary biologists debunked the hype. University of Minnesota-Morris Professor PZ Myers put it this way on his Pharyngula blog:
“She’s beautiful and interesting and important, but I do have to take exception to the surprisingly frantic news coverage I’m seeing. She’s being called the ‘missing link in human evolution,’ which is annoying. The whole ‘missing link’ category is a bit of journalistic trumpery: almost every fossil could be called a link, and it feeds the simplistic notion that there could be a single definitive bridge between ancient and modern species. There isn’t: there is the slow shift of whole populations which can branch and diverge.”
Wellllll. Ida actually came from an extinct group of primates that was more closely related to lemurs than to monkeys, apes and humans, the journal Nature reported this week.
To be sure, she shared features with higher primates.
But those features are an example of convergent evolution not direct lineage, said Erik Seiffert of Stony Brook University in New York who was the lead scientist on the research reported this week. In other words, the features evolved independently in unrelated creatures.
Seiffert’s conclusions are based on analysis of another fossil primate, Afradapis longicristatus, which lived some 37 million years ago in Egypt. Seiffert and his team concluded that Ida and this younger fossil both came from adapoids, a group more closely linked to lemurs than to humans.
You can read BBC analysis of Nature’s report here.
Humans: Inevitable or accidental?
Meanwhile, Ida plays into yet another controversy as an example of convergent evolution in which organisms from unrelated ancestors develop similar useful features. Take the wings of bats, birds and insects. They evolved independently, yet they serve similar purposes.
Here’s the controversy in a nutshell:
British paleontologist Simon Conway Morris and others argue that life evolves toward optimum ends. It’s an optimistic view, suggesting that evolution serves our understanding of progress. In that light, intelligence was inevitable, Morris claims. You can find a link here to one of his lectures on the inevitability of humans. In his lectures, Morris rests his arguments on example after example of beneficial features shared by organisms that evolved independently.
But Stephen Jay Gould famously argues in his book “Wonderful Life” that if the tape of life were rewound and played again, it could take a very different course because of chance. Humans might not appear at all in this theoretical second playing of life’s tape. In particular, Gould argued that the human brain was not an inevitable evolutionary adaptation but rather a by-product of natural selection. His was a pessimistic view of evolution in that it debunked the notion that life evolved along a ladder of progress.
Now Ida no doubt will serve Conway Morris’s side of the debate as yet another example of beneficial traits developing through convergent evolution.
Myers, the U of M biologist, is no fan of Conway Morris’ arguments. “Curse you, Simon Conway Morris!” Myers wrote in a commentary on Conway Morris’ book “Life’s Solution: Inevitable Humans in a Lonely Universe.”
It’s certainly likely that some properties of life are inevitable, Myers acknowledged.
“Conway Morris wants to go further, though, and considers a specifically human-like form and intelligence to be as certain as the appearance of critters that eat other critters,” Myers said. “This is a remarkable conclusion. When I look at the diversity and history of life on Earth, I see a paucity of forms that resemble us—we seem to be oddballs.”