Echoes of Design: Independent Origins of Echolocation in Bats and Dolphins Challenge Biological Evolution
I’ve been told that even the best writers rely on editors. At least that’s what the editors who work with me say—maybe it’s so I’ll accept their editorial changes without complaining. Regardless, working with editors has taught me a lot about writing. For example, I’ve learned it’s not a good idea to repeatedly use the same redundant, superfluous word over and over again.
Repetition doesn’t make for good writing, nor does it make much sense when it comes to biological evolution. For this reason, a recent discovery that highlights the emergence of echolocation (locating prey by sound waves) in bats and marine mammals challenges evolutionary thinking.
Chance governs biological and biochemical evolution at its most fundamental level. Evolutionary pathways consist of a historical sequence of chance genetic changes operated on by natural selection, which, too, consists of chance components. The consequences are profound. If evolutionary events could be repeated, the outcome would be dramatically different every time. The inability of evolutionary processes to retrace the same path makes it highly unlikely that the same biological and biochemical designs should appear repeatedly throughout nature.
The concept of historical contingency embodies this idea and is the theme of Stephen Jay Gould’s book Wonderful Life.1 To help clarify the concept of historical contingency, Gould uses the metaphor of “replaying life’s tape.” If one were to push the rewind button, erase life’s history, and then let the tape run again, the results would be completely different each time.
Yet, it looks as if evolution has repeatedly hit upon the same outcome, over and over again. As evolutionary biologists Simon Conway Morris and George McGhee point out in their respective books Life’s Solution and Convergent Evolution, identical evolutionary outcomes are a widespread feature of the biological realm.2 Scientists see these repeated outcomes (known as convergence) at the ecological, organismal, biochemical, and genetic levels. From my perspective, the pervasiveness of convergence justifies skepticism about evolution’s capacity to fully account for the history and diversity of life on Earth.
One of the most remarkable examples of convergence is seen in the independent origin of echolocation in bats and cetaceans. Research indicates that echolocation arose independently in two different groups of bats and also in the toothed whales. Undaunted by the widespread occurrence of convergence, evolutionary biologists assert that independent evolutionary outcomes result when unrelated organisms encounter nearly identical selection forces (e.g., environmental, competitive, and predatory pressures). According to this idea, natural selection then channels the random variations believed to be responsible for evolutionary change along similar features in unrelated organisms.
If this explanation is valid, then the genetic changes responsible for the independent emergence of echolocation in the chiropterans and cetaceans should be distinct. Presumably, the evolutionary pathways that converged on a complex biological system such as echolocation would have taken different routes reflected in the genomes. In other words, even though the physical traits appear to be identical (or nearly identical), the genetic makeup of the organisms should reflect an independent evolutionary history.
Yet, new work by researchers from Europe shows that over 200 regions in the genomes of echolocating animals display convergent changes.3 These changes take place in genes associated with hearing and deafness, and in some instances vision.
From an evolutionary vantage point, this result was unexpected. The researchers note: “Our genome-wide analysis shows that natural selection has acted on three echolocating lineages…to produce complex patterns of changes in protein sequence, including both divergent, and, more surprisingly, extensive convergent changes.”4 Joe Parker, the lead investigator, marveled, “We had expected to find identical changes in maybe a dozen or so genes, but to see nearly 200 is incredible.”5
Convergence and the Case for Intelligent Design
Though the idea of convergence fits awkwardly within the evolutionary framework, it makes perfect sense if a Creator is responsible for life. Instead of convergent features emerging through repeated evolutionary outcomes, they could be understood as reflecting the work of a Divine mind. The repeated origins of biological features equate to the repeated creations by an intelligent Agent who employs a common set of solutions to address a common set of problems facing unrelated organisms.
1. Stephen Jay Gould, Wonderful Life: The Burgess Shale and the Nature of History (New York: W.W. Norton & Company, 1990).
2. Simon Conway Morris, Life’s Solution: Inevitable Humans in a Lonely Universe, (New York: Cambridge University Press, 2003); George McGhee, Convergent Evolution: Limited Forms Most Beautiful (Cambridge, MA: MIT Press, 2011).
3. Joe Parker et al., “Genome-Wide Signatures of Convergent Evolution in Echolocating Mammals,” Nature 502 (October 10, 2013): 228–31.
4. Parker et al., 231.
5. “Genetic Similarities between Bats and Dolphins Discovered,” ScienceDaily (September 4, 2013); http://www.sciencedaily.com/releases/2013/09/130904132548.htm.