August 14th, 2024
Started this book yesterday. It begins with a preface and a general prologue which explain the book. This will be a book that begins with the Homo sapien and goes backward in time. It will look at the evolutional changes that separate us from other existing species. Each chapter will be a rendezvous where two branches have split, starting with chimps but going all the way back to single-cell organisms. Written like Chaucer, all species are pilgrims looking for the common ancestor. Fossils and DNA are the major, and often redundant, sources of evidence. He talked about triangulation but I sort of zoned out by then.
August 15th, 2024
The first chapter talks about humans’ most recent common ancestor. First, we are all related. On the evolutionary timescale, you can go back to a single individual mammal and his descendants eventually turn into humans. Likewise, his brother could be the ancestor of all dogs, while another brother has no living descendants. The odds of two creatures following the same evolutionary path that create indistinguishable humans is practically zero. So humans have a common ancestor up to a point in recent human history. Mathematical models show that for an isolated island with a small population, like Tasmania before European colonization, would have a common ancestor about 12 generations ago. That is LOG2(population), where population is 5000. That’s just a couple centuries ago. If you go back further, eventually all humans from that time will be related to all living humans or none. That is to say that we would be related to every individual commonly or not at all. For this same population it was only about 22 generations, hardly 1000 years ago. At some point the number of grandparents, doubling by two with every great-, exceeds the living population and thus we must be interrelated. On Earth, it’s not so simple. Migration events and physical barriers prevent breeding. However, we come from the same heartland. Since Australia is the most isolated, I guess America was also, the models tend to show that the common ancestor is from south or east Asia about 10k years ago. Note that this is not to say we all have shared DNA. As the generation gap increases, the odds of our DNA being inherited becomes zero. It theoretically halves, but in reality it is random. However unlikely, it is possible that my child could get no DNA from my father and only the DNA I have from my mother. So though we have a common ancestor, we may not all even have his or her DNA.
August 16th, 2024
The next bit is about some recent milestones in humanity. The first is the agricultural revolution. Not much is said here that isn’t said elsewhere. Humans slowly progressed to pastoralism and farming as hunter-gatherers accidentally made certain crops grow or herded animals in specific locations. Breeding for domesticity (if that’s the right word) would be accidental without an understanding of genetics. The interesting point is that breeding to make animals tame has other consequences. Probably because certain genes go together. Compare dogs to their wolf ancestor; they hardly look alike. The author brings up an interesting point of how we humans may have genetically changed as we became sedentary and domestic. One noticeably one is cultures with lactose tolerance, a genetic mutation which many humans don’t have (including me). That’s not including the problems from the less-varied diet and illnesses from high population density. But nomads don’t have air conditioning and books, so who wins? Then there’s a couple pages on Cro Magnons, which is another revolution. It with these guys that humans leave an interesting archaeological record. They left cave paintings and more items than stone tools, like bone instruments and probably decorations. We don’t know what sparked this creativity. Now we will go back to more archaic humans.
August 22nd, 2024
The past couple days have been heavy on genes and DNA. I feel like there should have been some sort of primer chapter on the scientific details. As it stands, the descriptions and information are poor and haphazardly given, I’ll have to look up some of this stuff on my own. In Eve’s Tale, we discuss a lot about genes. Out of the many inherited genes, only two are gender-biased: mitochondria and the Y-chromosome. Mitochondria is inherited from your mother, always, and Y is obviously from father to son. All genes have only one parent, one grandparent, etc, so they are more traceable I guess. Since all women have a mother and all men have a father, you could trace these two genes back far enough until it unites with a single woman (Eve) or a single man (Adam). These individual titles could pass to a more recent ancestor is a male-to-male or female-to-female line ends. While interesting, using a single gene is not a good way to prove ancestry, says the author. Somehow I guess they use genes to try to estimate when modern humans left Africa by seeing how they mutate over time. Maybe it’s not mutation but random recombination through breeding. Enough about that. The Neanderthal genome, at the time of the writing in 2016, showed that around 1-2% of Eurasian genes were inherited by Neanderthal and that about 40% of the Neanderthal genome could be found in modern man. Then a little fingertip was found in Russia that turned out to be a big find. This was from a young Denisovan girl, who must have been a branch related closer to Neanderthals. The ground up finger tip was able to provide the entire genome. The odd thing is that we see almost 8% of their genes in modern individuals in Oceania. That’s about it. Now back to Homo Erectus/Ergaster.
August 27th, 2024
I keep forgetting to write. Pretty busy and my home laptop is temporarily out of commission. We were at Neanderthals, then we jumped to 1 MYA for Homo Erectus. I don’t think anything interesting was discussed other than how fossils are made. Back to 2 MYA we see Homo Habilis and we discuss brain size. The idea is that for a sample of animals, be it vertebrates, mammals, or great apes, there will be a logarithmic trend for brain size and body mass (approximately 3/4 slope). Anything “above” this slope has a bigger than expected brain size for its mass. The average varies with the sample, and it should surprise no one that apes have larger average brain sizes per body mass than birds. Humans are above average and are practically at the same point as dolphins. Fossils are hard to get data from because we have few samples. It’s not good practice to use one skull for an entire species, but you have to use what you have. Over time, there is a fairly linear trend from Australopithenes through early Homo to us. I think we left Homo there and went to more ape-like men. This might be what I read today, not sure; I’m sort of cramming three days into one. I guess there are Australopithecus robustus and its cousins, robust ape-men, and more gracile ape-men who came before them. One of these slender apes was the famous Lucy. Her kind lived approximately 4 MYA and were short compared to us, but bipedal. There’s several famous gracile ape fossils, and I forget the name of the one we use to discuss bipedalism. Nevertheless, bipedalism is another mystery like brain increase. Why? We can only speculate. Odds are it has nothing to do with the motion itself; it’s not all that advantageous. Could be sexual. Could be for safety, i.e., you can see farther, though you can see far from a tree, too. One theory is that natural selection favored apes who could squat and forage more easily. This over time led to different skeletal features in which bipedalism was more comfortable. It definitely has negatives, like spine problems. This theory suggests that bipedalism precedes brain size increase. Bipedalism freed the hands, allowed food transport and tool use, etc. Some controversial fossils, Sahel tchadensis or something, may have been bipedal 6 MYA. This is when man and chimp when separate ways. A controversial theory is that chimps and gorillas “reverted” FROM bipedalism and our shared ancestor was bipedal. Or bipedalism evolved separately several different times. Who knows? Now we catch up with the chimps and bonobos.
August 28th, 2024
Now we leave the branch that is solely human and meet the common ancestor of man, chimp, and bonobo. This creature was probably more “proper” ape than humans are since humans are very different from the rest of the ape family. It probably was a forest animal like the chimp, ate fruit and sometimes hunted, walked with the aid of hands, and maybe even used tools. Chimps use tools and the interesting thing is chimps in different locations in Africa use different tools, that is they have different cultures. Bonobos, less studied, have not been seen to use tools except when taught in captivity. Sometime 5-7 MYA, this animal became isolated in different groups, probably based on some geographical feature, and these two groups then developed into different gene pools that became different creatures altogether. The way to determine age is based on different mutations in the genes. It might just be our lack of understanding, but most of the DNA is unused. When this “useless” DNA mutates, it does not impact the creature and thus it can reproduce and spread this mutation. The rate of mutation and the number of mutations then gives us an approximate age of separation. The 5-7 MYA estimate comes from some sort of blood antibody test. The molecular evaluation gives us about 10 MYA, which the author says is a fine discrepancy. Something poorly explained about the genetic split point being older than the genealogical. I don’t understand that at all. That was the Chimp’s tale.
October 25th, 2024
I finished this book. Obviously, I haven’t written anything during my time reading it. Part of it was due to being busy at work and home, plus my computer being down initially. Another aspect is the book itself. It doesn’t seem very conducive to daily entries. It’s almost as if it is a series of short articles with a linking theme as opposed to a unified narrative. I did enjoy it for the most part. I think my ignorance on DNA and genes and whatnot cost me a bit and there wasn’t much help by the authors. Maybe some diagrams would’ve helped. Other than that most things were very interesting.