Everyone is familiar with the striking ability of certain birds (such as parrots) to vocalize speech, much as humans do. Well, according to the new papers published in Science that I wrote about earlier, confirming that birds arose explosively, those vocalization abilities are the result of “convergent evolution” at both the morphological and genetic levels.
Nature News reports, “The authors also conclude that vocal learning may have evolved independently in the ancestors of parrots, hummingbirds and songbirds.” But this is about more than just birds. According to a Science Daily article about the technical papers, the genetic “convergent evolution” extends to birds and humans:
“We’ve known for many years that the singing behavior of birds is similar to speech in humans — not identical, but similar — and that the brain circuitry is similar, too,” said Jarvis, an associate professor of neurobiology at the Duke University Medical School and an investigator at the Howard Hughes Medical Institute. “But we didn’t know whether or not those features were the same because the genes were also the same.”
Now scientists do know, and the answer is yes — birds and humans use essentially the same genes to speak.
After a massive international effort to sequence and compare the entire genomes of 48 species of birds representing every major order of the bird family tree, Jarvis and his colleagues found that vocal learning evolved twice or maybe three times among songbirds, parrots and hummingbirds.
Even more striking is that the set of genes involved in each of those song innovations is remarkably similar to the genes involved in human speaking ability.
If you’re already thinking “This isn’t ‘convergent evolution,’ it’s common design,” you haven’t seen the best part yet. Science Daily goes on:
One of the Dec. 12 papers in Science found there is a consistent set of just over 50 genes that show higher or lower activity in the brains of vocal learning birds and humans. These changes were not found in the brains of birds that do not have vocal learning and of non-human primates that do not speak, according to this Duke team, which was led by Jarvis; Andreas Pfenning, a graduate of the PhD program in computational biology and bioinformatics (CBB); and Alexander Hartemink, professor of computer science, statistical science and biology.
“This means that vocal learning birds and humans are more similar to each other for these genes in song and speech brain areas than other birds and primates are to them,” Jarvis said.
These genes are involved in forming new connections between neurons of the motor cortex and neurons that control the muscles that produce sound.
The Science paper puts it this way:
More than 50 genes contributed to their convergent specialization and were enriched in motor control and neural connectivity functions. These patterns were not found in vocal nonlearners, but songbird RA was similar to layer 5 of primate motor cortex for another set of genes, supporting previous hypotheses about the similarity of these cell types between bird and mammal brains.
(Pfenning et al., “Convergent transcriptional specializations in the brains of humans and song-learning birds,” Science, Vol. 346: 1256846-1 – 1256846-13 (December 12, 2014). )
So certain birds and humans use the same genes for vocalization — but those genetic abilities are absent in non-human primates and birds without vocal learning? If not derived from a common ancestor, as they clearly were not, how did the genes get there? This kind of extreme convergent genetic evolution points strongly to intelligent design.
The authors of the paper are, to be sure, not ID advocates. Yet they acknowledge how big the problem of convergent genetic evolution is becoming for evolutionary biology:
We reasoned that one or more genes underlying a complex trait could show convergent evolution across species, even those separated by tens to hundreds of millions of years from a common ancestor.
For example, convergent identical amino acid substitutions have been identified in the opsin gene for light absorption across different vertebrate lineages; in the melanocorticotropin receptor in mammals and birds for skin and feather color, respectively; in a gene for yellow wing spots used for courtship in flies; in Pitx transcription factors for gain and loss of limbs in fish and marine mammals; in a sodium channel for electric organs in independent lineages of fish; and in the prestin gene for echolocation in bats and cetaceans. In addition, for echolocating mammals, genome-scale convergence in amino acid sequence was recently found in many genes involved in hearing. Likewise, convergent changes in amino acid sequence among vocallearning birds and mammals have recently been reported. However, we are not aware of examples of widespread convergence in gene expression patterns in brain regions involved in convergently evolved behavioral traits.
With the journal Aeon now reporting that “Genes that leap from one species to another are more common than we thought,” the whole “tree of life” hypothesis is really falling apart:
One of the most clear-cut instances of horizontal gene transfer is the story of the fungus and the pea aphid. Some fungi, plants and bacteria have genes encoding carotenoids, a diverse class of colourful molecules involved in everything from photosynthesis and vision to camouflage and sexual attraction. No one had ever found such genes in animals, though. In all known cases, animals acquired carotenoids from their diet (for instance, flamingoes become red and pink from eating plankton). In late 2009, Nancy Moran, an evolutionary biologist then at the University of Arizona, stumbled onto the fact that pea aphids have a carotenoid gene.
Evolutionary biologists try to retain the idea of common ancestry by explaining away such inconvenient data. They invoke processes like “convergent evolution,” “horizontal gene transfer,” “incomplete lineages sorting,” and others. How many epicycles can the tree of life accommodate before scientists widely acknowledge that the Darwinian model just isn’t working?