Over the summer, I hope to find time to read Neil Shubin’s book, Your Inner Fish:
Why do we look the way we do? What does the human hand have in common with the wing of a fly? Are breasts, sweat glands, and scales connected in some way? To better understand the inner workings of our bodies and to trace the origins of many of today’s most common diseases, we have to turn to unexpected sources: worms, flies, and even fish.
While these may be “unexpected sources” from the conventional, non-teleological perspective, readers of this blog know that this is the very type of thing we expect from my hypothesis of front-loading evolution.
Yes, this is all very cool that we can trace the inner workings of our bodies to the inner workings of fish, flies, and worms . But it’s better than this, folks. Remember the single-celled amoeba forming a multicellular life form before your very eyes?
The amoeba coalesce into multicellular life as a response to stress. What’s makes this so super cool is that they use the same circuitry the human body uses to respond to extreme stress: G protein receptor, G proteins, adenylyl cyclase, cAMP, and protein kinases. Humans use this circuit as part of their “fight and flight” response, where it is triggered by the hormone epinephrine (adrenalin). I don’t know if these amoeba make or use epinephrine, but others do.
Someday I may write a book entitled, Our Inner Amoeba as these continual findings of deep homology enhance the plausibility of my particular front-loading hypothesis.
BTW, I should also mention that such deep homology was not predicted to exist by the Modern Synthesis.
On the contrary, it was predicted to not exist.
When you think about all of the diversity of forms out there, we first believed this would involve all sorts of novel creations, starting from scratch, again and again and again. – Sean Carroll
Much that has been learned about gene physiology makes it evident that the search for homologous genes is quite futile except in very close relatives. If there is only one efficient solution for a certain functional demand, very different gene complexes will come up with the same solution, no matter how different the pathway by which it is achieved. The saying “Many roads lead to Rome” is as true in evolution as in daily affairs. – Ernst Mayr
And so to see that genes that are doing such profound things in the fruit fly — making head from tail, stomach from back, thorax from abdomen — are conserved, related in other animals … this was just not predicted by anybody. – Mike Levine
the adaptationist paradigm of evolutionary biology seemed to imply that genes, whatever their molecular nature, would not be well conserved between distant organisms – Eugene Koonin
The existence of “deep conservation” is a surprise. To some biologists it is a contradiction of their expectations about the organism’s capacity to generate random phenotypic variation from random mutations. To some, it borders on paradox when held against the rampant diversification of anatomy and physiology in the evolutionary history of animals. – Marc Kirschner and John Gerhart
Perhaps the most unexpected insight is exemplified by the fact that not a single biologist ever anticipated that the same genes controlling the design of an insect’s body and organs would also control the design of our own bodies. – Paul Brakefield
The most dramatic discoveries in evo-devo have been quite unexpected DNA homologies. It turns out that organisms as different as fruit flies and humans share considerable amounts of practically unaltered DNA, especially those stretches that are involved in development itself–ordering the rates and ways in which the parts of the body are formed (heads before legs and so forth). – Michael Ruse
Much of what we have learned has been so stunning and unexpected that it has profoundly reshaped our picture of how evolution works. Not a single biologist, for example, ever anticipated that the same genes that control the making of an insect’s body and organs also control the making of our bodies. – Sean Carroll