Common Design in Bat and Whale Echolocation Genes? - Evolution News & Views

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Common Design in Bat and Whale Echolocation Genes?

Last year I wrote about how convergent genetic evolution is highly unlikely under neo-Darwinism, but makes perfect sense if you allow common design. An article in ScienceDaily titled "In Bats and Whales, Convergence in Echolocation Ability Runs Deep," points to evidence that, in my opinion, might be best explained by common design.

According to the standard mammalian phylogeny, the common ancestor of bats and whales was not capable of echolocation. Thus, the ability to echolocate must have evolved independently, and bat and whale echolocation is often cited by evolutionists as a textbook example of convergent evolution. However, the ScienceDaily article reports that these similarities are not just phenotypic but extend down into the level of the gene sequences:

two new studies in the January 26th issue of Current Biology, a Cell Press publication, show that bats' and whales' remarkable ability and the high-frequency hearing it depends on are shared at a much deeper level than anyone would have anticipated -- all the way down to the molecular level
Just as I noted that convergent genetic evolution was said to be "surprising" under neo-Darwinian thinking, this article reports, "The discovery represents an unprecedented example of adaptive sequence convergence between two highly divergent groups and suggests that such convergence at the sequence level might be more common than scientists had suspected." The article continues:
"The natural world is full of examples of species that have evolved similar characteristics independently, such as the tusks of elephants and walruses," said Stephen Rossiter of the University of London, an author on one of the studies. "However, it is generally assumed that most of these so-called convergent traits have arisen by different genes or different mutations. Our study shows that a complex trait -- echolocation -- has in fact evolved by identical genetic changes in bats and dolphins."

[...]

"We were surprised by the strength of support for convergence between these two groups of mammals and, related to this, by the sheer number of convergent changes in the coding DNA that we found," Rossiter said

Likewise, a report by the same scientists in Current Biology called the finding "surprising":
Only microbats and toothed whales have acquired sophisticated echolocation, indispensable for their orientation and foraging. Although the bat and whale biosonars originated independently and differ substantially in many aspects, we here report the surprising finding that the bottlenose dolphin, a toothed whale, is clustered with microbats in the gene tree constructed using protein sequences encoded by the hearing gene Prestin.

(Ying Li, Zhen Liu, Peng Shi, and Jianzhi Zhang, "The hearing gene Prestin unites echolocating bats and whales," Current Biology, Vol. 20(2):R55-R56 (January, 2010) (internal citations removed).)

Thus, the high unlikelihood of such convergent genetic evolution poses great problems for systematists who seek to reconstruct a tree of life because molecular systematic banks upon the assumption that genetic similarity is the result of common inheritance. In this case, however, common inheritance makes no sense:
What could have caused the misplacement of dolphin to the bat clade in the prestin tree? Horizontal gene transfer, DNA contamination, gene paralogy, long-branch attraction, and biased amino acid frequencies are all unlikely. The only remaining reason is the convergence of the prestin sequences of echolocating bats and whales, likely resulting from a common selection for amino-acidaltering mutations that are beneficial to echolocation.

(Ying Li, Zhen Liu, Peng Shi, and Jianzhi Zhang, "The hearing gene Prestin unites echolocating bats and whales," Current Biology, Vol. 20(2):R55-R56 (January, 2010) (internal citations removed).)

A review of this research in Current Biology stated:
Remarkably, prestin amino-acid sequences of echolocating dolphins have converged to resemble those of distantly related echolocating bats. ... Even more remarkable is the new finding that echolocating dolphins and porpoises show Prestin gene sequences that resemble those of echolocating bats. Whales and dolphins belong to the order Cetartiodactyla, and their closest living relatives may be hippopotamuses. Nevertheless, dolphins and porpoises share at least 14 derived amino acid sites in prestin with echolocating bats, including 10 shared with the highly specialised CF bats. Consequently, dolphins and porpoises form a sister group to CF bats in a phylogenetic analysis of prestin sequences (Figure 1). This finding is arguably one of the best examples of convergent molecular evolution discovered to date, and is exceptional because it is likely to be adaptive, driven by positive selection.

(Gareth Jones, "Molecular Evolution: Gene Convergence in Echolocating Mammals," Current Biology, Vol. 20(2):R62-R64 (January, 2010) (internal citations removed).)

But given how "surprising" and "remarkable" this finding is to evolutionary biologists, perhaps it is likely to be driven by common design.