For Ceeboo: Whales, Hippos and Melatonin
Posted: Wed Oct 02, 2019 9:26 pm
The advantage that science has over religion as the basis for a worldview is that science isn't afraid to refine its views in the light of new data. And here are some new data for Ceeboo, who has expressed great concern in the past as to just how raccoon-like land mammals could have evolved into whales.
A recent NPR Science Friday podcast described the evolution of land mammals to whales on a molecular genetic level by cross comparisons several whale species genomes to those of likely related land mammals (according to the fossil record).
Finding number one? The closest land mammal genetically to whales is not the raccoon, as might have been suggested by the fossil record. Genetics indicates that the most closely related land mammal to whales is the hippopotamus. Whales branched from the ancestors of hippos, and returned to the salt water sea long before the baleen whales branched from the toothed whales some 30 million years ago.
Scientists then looked for the genes that had been altered in the whales (and other cetaceans) as compared to their distant land mammal relatives. They found approximately 85 land mammal genes that had been inactivated, broken, or had the timing of their expression altered in the whale. Inactivated or broken "fossil" genes included those that coded for the proteins that help make saliva, hair, and most interestingly- the sleep hormone melatonin.
In order to keep from drowning or suffering from hypothermia, cetaceans can only afford to allow half of their brain to sleep and any given time. They need to have sufficient brain function at all times to control body movements required to breath, maintain body temperature and detect predators.
Since the entire brain is never asleep at the same time, having a sleep hormone like melatonin flooding the entire brain could be dangerous, so the gene that makes melatonin from serotonin has been completely deactivated.
So, no more jokes about raccoons to whales, now its hippos to whales. Hopefully Ceeboo finds this bit of scientific progress easier to accept.
A recent NPR Science Friday podcast described the evolution of land mammals to whales on a molecular genetic level by cross comparisons several whale species genomes to those of likely related land mammals (according to the fossil record).
Finding number one? The closest land mammal genetically to whales is not the raccoon, as might have been suggested by the fossil record. Genetics indicates that the most closely related land mammal to whales is the hippopotamus. Whales branched from the ancestors of hippos, and returned to the salt water sea long before the baleen whales branched from the toothed whales some 30 million years ago.
Scientists then looked for the genes that had been altered in the whales (and other cetaceans) as compared to their distant land mammal relatives. They found approximately 85 land mammal genes that had been inactivated, broken, or had the timing of their expression altered in the whale. Inactivated or broken "fossil" genes included those that coded for the proteins that help make saliva, hair, and most interestingly- the sleep hormone melatonin.
In order to keep from drowning or suffering from hypothermia, cetaceans can only afford to allow half of their brain to sleep and any given time. They need to have sufficient brain function at all times to control body movements required to breath, maintain body temperature and detect predators.
Since the entire brain is never asleep at the same time, having a sleep hormone like melatonin flooding the entire brain could be dangerous, so the gene that makes melatonin from serotonin has been completely deactivated.
So, no more jokes about raccoons to whales, now its hippos to whales. Hopefully Ceeboo finds this bit of scientific progress easier to accept.
