First, we are not talking about the supposed pig-chimp hybrid that allegedly produced humans (and was taken seriously by some), nor the similar idea suggested for caterpillars in the National Academy of Science’s publication PNAS, for which idea Scientific American promptly dubbed PNAS the “National Enquirer” of the sciences.
All that said: Hybridization might still be a viable idea for evolution—if strictly limited to probable situations, and not invoked to solve otherwise intractable problems.
Okay, here from ScienceDaily:
Scientists have detected at least three potential hybridization events that likely shaped the evolutionary paths of ‘old world’ mice, two in recent times and one in the ancient past. The researchers think these instances of introgressive hybridization — a way for genetic material and, potentially, traits to be passed from one species to another through interspecific mating — are only the first of many needles waiting to be found in a very large genetic haystack. While introgressive hybridization is thought to be common among plants, the finding suggests that hybridization in mammals may not be the evolutionary dead end biologists once commonly thought.
Nakhleh said other studies may have missed evidence of hybridization because the researchers weren’t specifically looking for it. “Why is it that biologists in general who look at mammalian genomes haven’t found hybridization? I think it’s because they started with the hypothesis that it couldn’t be there and used tools that would ignore it.
But note, they are all still mice, and no obviously counterfactual claims are made here concerning mice.
Here’s the abstract:
We report on a genome-wide scan for introgression between the house mouse (Mus musculus domesticus) and the Algerian mouse (Mus spretus), using samples from the ranges of sympatry and allopatry in Africa and Europe. Our analysis reveals wide variability in introgression signatures along the genomes, as well as across the samples. We find that fewer than half of the autosomes in each genome harbor all detectable introgression, whereas the X chromosome has none. Further, European mice carry more M. spretus alleles than the sympatric African ones. Using the length distribution and sharing patterns of introgressed genomic tracts across the samples, we infer, first, that at least three distinct hybridization events involving M. spretus have occurred, one of which is ancient, and the other two are recent (one presumably due to warfarin rodenticide selection). Second, several of the inferred introgressed tracts contain genes that are likely to confer adaptive advantage. Third, introgressed tracts might contain driver genes that determine the evolutionary fate of those tracts. Further, functional analysis revealed introgressed genes that are essential to fitness, including the Vkorc1 gene, which is implicated in rodenticide resistance, and olfactory receptor genes. Our findings highlight the extent and role of introgression in nature and call for careful analysis and interpretation of house mouse data in evolutionary and genetic studies. – Kevin J. Liu, Ethan Steinberg, Alexander Yozzo, Ying Song, Michael H. Kohn, Luay Nakhleh. Interspecific introgressive origin of genomic diversity in the house mouse. Proceedings of the National Academy of Sciences, 2014; 201406298 DOI: 10.1073/pnas.1406298111
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