I imagine that the changes would have occurred gradually and in parallel, consistent with what is know about evolution. Just looking on google, I note elephants also have internal testes. I never realized that I had never seen an elephant scotum, because they don’t exist. Evidently it sort of depends on the relative risks of exposure vs cooling, and in fact scotums probably evolved from animals with internal testes.
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You are right. There are actually a lot of terrestrial animals with internal testes, including hedgehogs, tapirs, moles, rhinos, anteaters, etc. There is a hypothesis that certain motions like galloping and bounding put too much pressure on the testicles, making their externalization an advantage. I found this informative article in Slate: The Scrotum is Nuts
Great article, beaglelady. Amazing what you never knew you didn’t know.
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Has anybody in the ID movement discussed any of this with whale evolution expert Philip Gingerich? His web page on whales is here.
With the level of redundancy observed in mammalian systems that regulate gene expression, I would suspect that it is quite unlikely that a single gene is responsible for the regulation of either system, let alone both. Certainly, it is possible that INSL3 is involved in regulating both processes, but INSL3 works in coordination with a variety of other regulatory factors such as Inhibin B, AMH, SF-1, and testosterone. INSL3 is also an important factor in fish (and maybe other animals), suggesting a rather conserved function and not specialized for whales.
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The cooling system is a countercurrent exchanger. It’s cool (heh) but it’s not highly complex; it’s basically just proximity of veins and arteries, with outgoing and incoming blood kept close. Don’t get me wrong: it’s interesting. But it’s not an elaborate “cooling system”–it’s just an altered arrangement of blood vessels so that cool blood from extremities flows near testes in cetaceans. The system did not have to be invented by cetaceans, since it’s a conserved mechanism in all mammals, used most famously in the kidney (to concentrate urine) but also in the skin and the core. This has been known for a very long time. Its genetic basis is just being understood: a 2015 paper in Developmental Cell showed that a signaling protein called Apelin is necessary for the artery/vein patterning that creates countercurrent exchange. Mice lacking the protein (or its receptor) have problems with thermoregulation, and this tells you that the suggestion of a unique cetacean “cooling system” is wrong (more accurately, it’s uninformed).
APJ Regulates Parallel Alignment of Arteries and Veins in the Skin
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Thanks very much Steve! I’m also suspicious of talk about several mutations having to occur at the same time. That’s a familiar refrain from the ID movement. There is usually plenty of existing variation in populations of animals.
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Hi Stephen,
Thanks very much for the article on apelin, and for the information about how the cooling system is a conserved mechanism in mammals. I think the evidence you’ve presented undercuts the argument that two mutations had to occur simultaneously in the evolution of whales. Cheers.
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Hi beaglelady,
As far as I know, they haven’t. I might get in touch with him myself. Thanks very much for the link to his Webpage on whales.
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I’d like to second what Jim said. The Slate article was highly informative. Thanks again, beaglelady.
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Hi Vincent,
That evidence does undercut the testes/cooling story as an argument for extremely fast or extraordinary evolutionary change. But I think the more basic problem is that the arguments were advanced without any evidence, indeed without any reported attempt to obtain evidence.
It may very well be that there are aspects of the whale evolution trajectory that are peculiar enough to require extraordinary explanation. For at least some of these aspects, there are available data (genomics, anatomy, paleontology, physiology) that could be analyzed to look for abrupt changes. There are places to publish such analyses, even in progress, to get feedback and critique from other experts. There are lots of scientists who, like me, would be very interested in such work. It doesn’t seem that Sternberg is doing any of it. That’s a shame.
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I didnt even know who Paul Nelson was…
But apparently he visited BioLogos for a few days and never posted a thing…
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How did you get entangled into this argumentative aspect of whale evolution? As soon as he said ten million years… I knew he wasn’t defending the YEC position.
But what position is he really defending… especially if he is a Pythagorean?
You are very welcome. Whale evolution is fascinating.
Hi George,
The term “creationist” (which you use in the title of your piece) is a very broad one. It certainly includes old-earth creationism. I wouldn’t call Sternberg a creationist, but I do know that there are quite a few old-earth creationists in the Intelligent Design movement, and they are fond of citing Sternberg’s writings on whale evolution in support of their position that the first “true whales” (Basilosaurids) were created by the agency of God. Many of them would dispute the notion that the Basilosaurids were descended from the protocetids, which they regard as fundamentally different.
Wait, what? You are telling me that people who believe the Earth is way older than 6000 years… and that walking proto-whales evolved in 10 million years… reject the idea of common descent from protocetids?
Are you saying
[1] that they think Basilosaurids descended from a different lineage?
Or, are you saying
[2] they reject that Basilosaurids descended from any other whale lineage?
Which seems ridiculous, since most of the major morphological differences studied to date have turned out to be caused by loss-of-function alleles. IIRC the major differences in the genomic sequences between cetaceans and their closest terrestrial relatives are duplications, not suggestive of “coordinated mutations.”
Do they even go into the genomic data?
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There is apparently a part 3 of the podcast series, and I have not watched the YouTube video with Nelson (linked above somewhere by @vjtorley) or watched the DVD. So it is possible that they looked at data (any data). From what I heard, I thought it was clear that they have done no analysis of any kind, on genomic data or any other data from cetaceans. The argument amounts to “whale evolution was fast, I don’t see how it could have all happened,” accompanied by a list of physiological differences that we know to be exaggerated (see discussion of countercurrent exchange above).
It’s hard to tell whether anyone at the DI has the expertise to look for lineage-specific genomic changes.
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