CapitalistImperialistPig

Things to think about: Mice are rodents, and the rodent and primate lines separated a long time ago, probably on the order of about 75 million years ago. Mice are small-brained; they possess a neocortex but it is much smaller relative to that of primates, and, of course, minuscule in comparison to ours. Yet, comparison of mouse and human genomes reveals that greater than 99 percent of all genes in the human have a mouse counterpart, and vice versa. In fact, 96 percent of all genes in the human are found in the exact same relative order in human chromosomes as in the mouse chromosomes. This is a remarkable degree of similarity. These figures tell us that in the course of 75 million years of mammalian evolution, and at least 55 million years of primate evolution, our genome and that of a rodent contain essentially the same genes in mostly the same organization. Carroll, Sean B.. Endless Forms Most Beautiful: The New Science of Evo Devo (pp. 269-270). W. W. Norton & Company. Kindle Ed...

Most of the familiar animals (bears, people, fish, insects, worms, squid, snails, starfish) are members of the bilateria , bilaterally symmetric animals with front and back, top and bottom. Most of them are either deuterostomes (e.g., us, fish, starfish) or protostomes (arthropods, worms, clams, squid). They all develop from an egg which divides and forms a hollow ball of cells which dents in during gastrulation and ultimately penetrates to the other side, forming the gut. In deuterostomes, the original dent becomes the anus. In protostomes, it either becomes the mouth (or according to some) both mouth and anus. One of us seems to have got it backwards. How did that happen?

Yeah, I know about the Vikings. But there are some earlier and (to me) more remarkable voyages. Consider the case of the New World Monkeys. Monkeys first evolved about 50 million years ago, in Africa. Somehow, about 30 million years ago, some of them (or maybe just one of them) managed to cross the Atlantic Ocean to South America. Recall that Gondwana, which included Africa, South America, Antarctica, India, and some other stuff split up about 180 million years ago (mya), with Africa and South America parting company about 130 million mya. The Atlantic was narrower than now 30 mya, but still at least 1000 miles wide. While it's possible that some mid-ocean islands existed, pretty extensive sailing, or rather rafting, was still required. Alan de Queiroz has written a book about it, and has a shorter account of it here in The Huffington Post. Many other creatures seem to have made similar voyages. This story and others like demonstrate why evolution can't really be a p...

I have been taking Yuval Noah Harari's Coursera course A Brief History of Humankind , which takes a long term view of the human story. Prof Harari is very much of the evolutionary point of view, and he frequently emphasizes that some of the deepest puzzles of human history are posed by those evolutionary questions. What, for example, is the point of a big brain if you have only the most primitive tools and weapons, and are stuck down somewhere in the middle of the food chain. It's three per cent or so of our body weight costs us 25% of our energy usage, for example, and it is burdensome to carry around with all their accompanying packaging. Everything in evolution, he likes to say, has a cost. We pay for the big brain by needing to eat more and by sacrificing much of our muscles. We are incredibly puny, for example, compared to a chimpanzee of the same weight. One argument he makes that I find less persuasive - so far, anyway - is that because humans have been top predator...

Caught an interesting Nova episode tonight.  It featured a detailed look at the first five million years or so of human evolution, starting with our first bipedal ancestors six or so million years ago.  A plausible argument was made that bipedalism was an adaption to the gradual drying of the African continent, requiring more efficient walking - it seems that humans expend about 1/4 as much energy per distance walked as a chimp. Human like biped species proliferated over the next 3-4 million years, but their brain sizes stayed pretty close to chimp size (400cc) - roughly 1/4 the size of the modern humans.  At that point a period of violent climate change began, with the climate swingly wildly from tropical jungle to near desert over very short periods of time (on the thousand year scale).  Lake Victoria size lakes would form and then completely,  or nearly completely, dry up.  That period is poor in human fossils, but at the end of it a new type of h...

The toughest problem in defining a general theory of life is the paucity of examples. That statement sounds like an oxymoron - isn't life famously diverse? Man, elephant, mouse, carrot, redwood, mushroom, coral, sponge, and bacterium seem pretty darn different. At the molecular level, however, they aren't. The most essential machinery at the molecular level is almost exactly the same. They all use the same genetic code, and the same basic mechanisms for the most basic operations of life. These commonalities, and the patterns of both commonalities and differences constitute the most dramatic proof of the fact of common descent. However all that common machinery came into existence, it all seems to have existed in the most recent common ancestor of all known Earthly life. Despite a large number of apparently contingent and arbitrary elements in life, exceptions are not known. Proteins and complex sugars have definite chiralities but we don't know of any fundamental r...

A bar I once knew was frequented by, among others, loggers and college football players. Oddly enough, this occasionally led to strife. Usually one doesn't notice the precipitating event, but the denouement stuck in my mind. Football guy: ...You're just a dumb truck driver. The logger (or maybe logging truck driver), responded with a physical riposte, and football guy was soon on the floor, oozing blood. Football guy: You're still a dumb truck driver. Logger: Maybe so, but if you're so smart, how come you are looking up at me from the floor bleeding? Rhetoric isn't what it once was.

Andrew H. Knoll's Life on a Young Planet: The First Three Billion Years of Evolution on Earth is one of those rare books that can change your, or at any rate, my, picture of reality. I have posted twice before on this book: Eu are Irrelevant and In the Beginning , but the present post is my attempt at a review. Dinosaurs and mastodons don't wander through these pages, unless you count a cameo or two. Their time was still far in the future when the characters whose story is told here held center stage. The Cambrian Period, which started about 543 million years ago, or a bit less than ten thousand times as long ago as our own species originated, ushered in the Paleozoic Era and the first easily recognizable fossils. It was the first age of animals - not the very first animals, but the first animals with considerable size and complexity. All the animal phyla we now recognize were onstage in the Cambrian, as well as numerous phyla dead and gone. Before the Cambrian, only sponges,...