Marvels of Evolution

I'm reading a recently published work by famed evolutionary biologist Richard Dawkins, THE GENETIC BOOK OF THE DEAD. The title refers to this book's dominant metaphor of a palimpsest, a document whose text has been written over, sometimes more than once. On a literal palimpsest, the original words have been obliterated by the later ones. That isn't the case with the genetic, anatomical, physiological, and behavioral traces that reveal the ancestral past of animals and other living creatures, so the metaphor isn't perfect (as Dawkins notes) but still makes a fruitful device for contemplating the evolution of life on Earth. As the cover blurb puts it, every creature can be regarded as "an archive of the worlds of its ancestors." What do an animal's body structure, genome, and behavior inform us about the environment that shaped it?

Naturally, it's easy to tell a herbivore's skull from a carnivore's by their teeth. We can learn much more about the past of various species by observing present-day creatures, though. A lizard with skin like rocks and sand must have descended from ancestors that lived in a desert; the forebears of insects that look like twigs must have evolved in trees. Many other types of visual deception exist, some truly weird. The "palimpsest" can tell us about animals whose predecessors left the ocean to become land-dwellers, returned to the sea, and some cases even developed back into terrestrial animals. Convergent evolution can result in animals that look uncannily similar although not at all closely related, because they've developed to fill the same kinds of environmental niches. One page illustrates a variety of marsupials alongside their placental mammal counterparts, some almost indistinguishable to a casual glance. "Divergent" evolution, on the other hand, concerns closely related species that have developed so differently in different habitats that they look nothing alike, e.g., whales and hippos. And those topics take us less than halfway through the book. In an exciting twist in the final chapter, for instance, we learn that we may have acquired a nontrivial portion of our genes from ancient viruses.

For another mind-blowing work by Dawkins, check out THE ANCESTOR'S TALE. This one adopts its metaphor from Chaucer's THE CANTERBURY TALES, which portrays a group of pilgrims coming from far and wide to unite and travel together. Beginning with modern humans, Dawkins follows the evolution of life backward by successive stages to each most recent common ancestor -- our common ancestor with other hominids, then the shared progenitor of hominids and other apes, through primates, placental mammals, etc., back to the hypothetical original ancestor of all life on our planet. Of course, as the author points out, no matter what modern-day creature we start from, we ultimately end up at the same point. He starts with Homo Sapiens simply because that's us. THE ANCESTOR'S TALE is the most comprehensive survey of the development of life on Earth I've ever read.

Some animals and plants are so odd -- to human observers -- that an SF author wouldn't need to search far to discover concepts for bizarre aliens right here on our world. Reverting to THE GENETIC BOOK OF THE DEAD, I find the chapter on convergent evolution particularly interesting. It's often claimed that if life exists on other planets, the inhabitants won't look anything like earthlings. But why not? If we discover a planet with geography, climate, gravity, and atmosphere similar to Earth's, couldn't those environmental conditions lead to the development of organisms that strongly resemble the plants and animals we know? Biological constraints work the same everywhere on Earth, so why not on other Earth-like planets? There could even be humanoid or quasi-humanoid intelligent beings on such a world.

Margaret L. Carter

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Biology Marches On

I'm currently reading, little by little, a book by evolutionary biologist Richard Dawkins (best known for THE SELFISH GENE), THE ANCESTOR'S TALE: A PILGRIMAGE TO THE DAWN OF LIFE. He structures the book by analogy with THE CANTERBURY TALES, with "pilgrims" joining the procession at various rendezvous points, backward from the most recent progenitors of humanity to the origin of life on Earth. At each "rendezvous," he introduces our "concestor" at that juncture, a coinage for "common ancestor." For instance, we meet the common ancestor of all known hominids, of hominids and other primates, of primates and other mammals, etc. One fascinating revelation of this book, for me, is how the classification of life on Earth has changed since my time in public school. In the 1950s and 60s, biology classes taught us to divide all creatures into two kingdoms, animals and plants. Bacteria, amoebae, and fungi got pigeonholed with plants, while protozoa qualified as animals. Today, biological science recognizes up to six kingdoms: Animals, Plants, Fungi, Protista, Archaea/Archaebacteria, and Bacteria/Eubacteria). Amazingly, according to Dawkins, fungi are more closely related to animals than to plants! Here we see an example of the trope "Science Marches On" (i.e., it's always possible for yesterday's established theories to be revised or replaced).

Similarly, during our elementary and high-school years (shortly after dinosaurs roamed the Earth), all humanity consisted of three races, then called Caucasoid, Mongoloid, and Negroid. The song we learned in Sunday school about God's love for "all the little children" classifies them into "red and yellow, black and white." The three-race system of categories lumped "red" (Native Americans) in with the Mongoloid (Asian) ethnicities, not unreasonable considering the probable Asian origins of the original inhabitants of the Americas. If Inuits had been mentioned, they would probably have been included with the Mongoloid groups. Polynesians and other Pacific Islanders weren't brought up at all, much less Australian Aborigines and the Ainu of Japan. Aside from the fact that "race" in the old-fashioned sense is no longer considered a valid scientific category anyway, the ethnic divisions of Earth's population are more complicated than we were taught as children. A popular-culture example of unquestioning acceptance of the three-race system appears in James Michener's TALES OF THE SOUTH PACIFIC. (It's not quite explicit in the movie, although "You've Got to Be Carefully Taught" makes the implications clear enough.) When Nellie discovers that her French suitor has fathered illegitimate children by a Polynesian woman, she's appalled because, in her Southern world-view, there are only three races—white, Oriental, and Negro. Polynesians obviously don't belong to either of the first two, so they must be the third. (She uses the other N-word, however.)

Theories of the ancestry and origins of humanity have changed radically in recent decades, with new fossil discoveries and cutting-edge technology for detailed DNA studies of population movements. The film 2001: A SPACE ODYSSEY looks charmingly naive nowadays, with its dramatic scene based on the simplistic, now-abandoned assumption that our development into sapient beings sprang from our learning how to make weapons in order to kill things. (Elaine Morgan, in THE DESCENT OF WOMAN, labels this anthropological construct the "Tarzanist" theory.)

Coincidentally, I'm now rereading a duology by Rose Estes, TROLL-TAKEN and TROLL-QUEST. This fabulous urban fantasy (published in the 1990s) portrays the creatures we call "trolls" as descendants of Homo erectus, driven underground by the worldwide dominance of Homo sapiens. One of my favorite contemporary vampire series, S. M. Stirling's Shadowspawn trilogy (A TAINT IN THE BLOOD and sequels), postulates that his vampire-werewolf-sorcerer subspecies split off from "normal" humanity during a long period of isolation in the last Ice Age (a motif borrowed from Jack Williamson's classic DARKER THAN YOU THINK and updated with allusions to modern genetics and quantum mechanics). As reported in recent news, many scientists now believe that other hominids such as Neanderthals and the "hobbits" probably coexisted with and may have interbred with Homo sapiens. Keeping informed on latest developments in biology and anthropology can help authors create realistic, believable alien species.

Margaret L. Carter

Carter's Crypt