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from the am-I-going-to-regret-releasing-this? dept.
EurekAlert have just published an article: Yale researchers shed light on evolutionary mystery: Origins of the female orgasm
The role of female orgasm, which plays no obvious role in human reproduction, has intrigued scholars as far back as Aristotle. Numerous theories have tried to explain the origins of the trait, but most have concentrated on its role in human and primate biology.
[...] Since there is no apparent association between orgasm and number of offspring or successful reproduction in humans, the scientists focused on a specific physiological trait that accompanies human female orgasm -- the neuro-endocrine discharge of prolactin and oxytocin -- and looked for this activity in other placental mammals. They found that in many mammals this reflex plays a role in ovulation.
(Score: 5, Informative) by rleigh on Monday August 01 2016, @11:45PM
We don't have beaks at any point in development. Organisms with beaks are not ancestors of mammals, and we don't have the genes for a beak. (However, organisms with beaks do have organisms with teeth as ancestors, retain the genes for teeth since they are needed during development for other purposes, and they can under some circumstances grow teeth instead of a beak; this is possibly where the expression "rare as hen's teeth" comes from. http://www.sciencedirect.com/science/article/pii/B9780123971906000110) [sciencedirect.com]
Mammals do have gills, or at least an approximation of their structure, transiently during development. Fish are a common ancestor of mammals and birds. The pharyngeal arches are in mammals the source of special cell types which go on to form specific structures and organs. For example cells of the the third pharyngeal pouch migrate down to the top of the thorassic cavity, where they become the thymus, the organ used for T cell development and selection. Also, the repeated muscle blocks found in fish (somites) are also found in developing mammalian embroyos; but rather than staying put in the pattern found in the fish, they migrate around the embryo in a highly regulated fashion to form the musculature of the body, as well as bones, tendons and other tissues. http://www.embryology.ch/anglais/mmuskel/skelett01.html [embryology.ch] There are also other examples of this sort. The plan of something approximating a fish does exist transiently during the early stages of development, and is part of the first steps in the complex patterning of the mammalian body plan.
The above are are long-established developmental biology facts; you can see this stuff simply through observation of the growing embryo. I was taught this in my undergraduate and studied the development of the vascular system in lymphatic organs for my PhD. The most common model organism used to study mammalian vascular development is the zebrafish (Danio rerio). More evolved organisms augment the developmental pattern of their more primitive ancestors rather than replacing it. And most of the growth factors, inhibitors and signalling molecules are the same and can be used across species. And this makes evolutionary sense. A gene might mutate or be copied, but the need for the original function remains. More evolved organisms tend to conserve the function of genes found in their evolutionary ancestors since they are often critical to their viability, and this extends to development. It's easier to add new (copied) genes, and refine developmental processes by subtly adding to the process, than it is to change them wholesale. And this is where the "developmental hourglass" concept comes from. http://10e.devbio.com/article.php?id=343 [devbio.com]
Webbing as you say is due to a lack of cell death between fingers and toes. A single FGFR2 gene mutation can make the difference between webbed and not webbed. https://ghr.nlm.nih.gov/condition/apert-syndrome [nih.gov] so it's likely some modulation of FGF activity here was the cause of the loss of webbing in our amphibian ancestors.