I am fairly confident that the picture painted by the evolutionary psychologists is true. But I am also confident that it is not the whole truth, and that it leaves out of account precisely the most important thing, which is the human subject. We human beings do not see one another as animals see one another, as fellow members of a species. We relate to one another not as objects but as subjects, as creatures who address one another “I” to “you” — a point made central to the human condition by Martin Buber, in his celebrated mystical meditation “I and Thou.”I am less confident in the picture painted by evolutionary psychologists, because it amounts mostly to speculation without much solid evidence. That there has been biological change over time is obvious, but I am not altogether sure if we really understand the mechanics of that change. Showing how a given hypothesis might explain it is not the same as demonstrating that it does explain it. And no, I do not subscribe to Intelligent Design theory.
Friday, March 10, 2017
Good question …
… If We Are Not Just Animals, What Are We? - The New York Times. (Hat tip, Dave Lull.)
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With all due respect, the mechanics of biological change over time are very well understood. The past 40 years has seen huge growth in understanding of the genetic complexity underlying the variation that serves as the raw material for the evolutionary process.
ReplyDeleteThe importance of regulatory genes is one example. Take the FOXP2 gene, which is necessary but not sufficient for language capacity in humans. Individuals with mutations in the FOXP2 gene cannot acquire language, but appear cognitively normal in other respects.
The human version of the FOXP2 gene differs from the chimpanzee version by two nucleotides, a tiny structural difference. But this small change has huge functional consequences: the human FOXP2 gene increases the expression of 61 additional genes whose expression is not activated by the chimpanzee version. The genes activated by human FOXP2 are involved in development of the speech areas of the brain as well as of the soft tissue structures and muscles necessary for speech articulation. This is known as a gene cascade, where a small change in a single gene has broad downstream genomic effects. In this case it accounts, at least in some small part, for the difference in language capacity between chimps and humans.
Metaphorically speaking, some genes are foot soldiers while others are generals, whose function is to control large numbers of subordinate genes. Just as a change in general can affect the outcome of a battle and even the fate of a nation, a change in a regulatory gene can cause the kind of large phenotypic changes necessary for appearance of a new species.
The discovery of regulatory genes is just a single example, among hundreds, of the new knowledge that is deepening our understanding of the genotypic variation underlying biological change through time.
Jeff, can you suggest a layman-oriented book (or series of articles) which can explain recent developments in genetics well? I have a professional reason for asking. Thanks!
ReplyDeleteHi Jeff,
ReplyDeleteWell, thanks for that. You obviously know vastly more about that than I. One question, though. Given that "a change in a regulatory gene can cause the kind of large phenotypic changes necessary for appearance of a new species," should not new species be appearing on a regular basis? And if not, why not? Has evolution reached a certain point beyond which new species are unnecessary? It may well be a dumb question, but I'm a journalist. Dumb questions are my stock in trade. I also don't understand how the mechanics of genes go to explain individual psychology, which I presume is what evolutionary psychology purports to address. Oh, and I second Lee's request.
Frank and Lee,
ReplyDeleteSorry for the delay in responding, but it's been a busy weekend and I wanted to give some careful thought to the book recommendations. My top choice, by a whisker, would be 'Endless Forms Most Beautiful: The New Science of Evo Devo' by Sean B. Carroll. It begins with a somewhat breakneck tour through the histories of evolution science, genetics, and developmental biology, but then settles into a fascinating narrative about how these three areas of study came together in the early 1980's and started yielding truly surprising data about how new animal forms arise.
An equally good but less detailed book, focused more narrowly on variation in human anatomy, and especially on how scientists have thought about such variation throughout history, is 'Mutants: On Genetic Variety and the Human Body' by Armand Marie Leroy. (A crappy title for a well-written book aimed at introducing modern biological thought to the layman!) There is some overlap with the Carroll book, particularly in coverage of homeotic genes, a critical topic.
If I can find some relevant summary articles about these areas of research, I'll forward by e-mail.
Notice that I've left out any books that discuss the evolution, genetics, and developmental biology of plants, which is my area of professional expertise. I've done so for three reasons: these processes differ greatly between plants and animals, and adding a book about plants would just sow confusion (sorry for the bad pun!); much less has been written about plant molecular biology; most people are just more interested in animal biology, especially human biology.
Frank, your questions are not dumb at all! Speciation, evolution of complexity (which you've mentioned before), and "evolutionary psychology" are three of the most active areas of research in evolutionary biology. (My use of scare quotes should give you some idea of what I think about the more grandiose claims of "evolutionary psychology").
The answer to your question about speciation is that new species are, in fact, appearing on a regular basis. 23,000 years ago, a new lake was created in what is now Nicaragua by an earthquake-induced rockslide that dammed a small stream. The stream contained a single species of fish from the cichlid family, a species that fed on insect larvae on the water's surface and had the shiny, reflective coloration that provides camouflage for surface-feeding fish, protecting them from bird and mammal predation. That species still exists in the surface waters of the lake, but a new species has diverged from the first during the intervening millennia. This second cichlid species lives on the lake bottom, has the dark coloration characteristic of bottom-dwelling species, and has evolved modified mouth parts that allow it to crack open snail shells, allowing it to feed on the soft tissue inside. It also has a more tubular shape than its flattish surface progenitor, which allows it to better withstand the much greater water pressure at the lake bottom. 23,000 years may seem like a long duration for a speciation event, but the interval needs to be viewed in geological time. Evidence for the first life on earth dates to 3.5 billion years ago. If you condense that to a single year, then 23,000 years becomes three minutes. That new fish species appeared at 11:57 PM on December 31 of the Year of Life on Earth. Homo sapiens appeared at around 11:30 PM on December 31.
Speciation is still happening; it's just too slow for us to see on a human scale, requiring tens to hundreds of thousands of years to reach completion.
I hope at least some of this is interesting!