Wonderful Life (Part VII, FINAL)
Mar. 24th, 2005 01:11 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
prof_pangaeaExcerpt from:
Wonderful Life: The Burgess Shale and the Nature of History
by Stephen Jay Gould
VII. The Origin of Homo sapiens
I will not carry out this argument to ridiculous extremes. Even I will admit that t some point in the story of human evolution, circumstances conspired to encourage mentality at our modern level. The usual scenario holds that attainment of upright posture freed the hands for using tools and weapons, and feedback from the bahavioral possibilities thus provided spurred the evolution of a larger brain.
But I believe that most of us labor under a false impression about the pattern of human evolution. We view our rise as a kind of global process encompassing all members of the human lineage, wherever they may have lived. We recognize that Homo erectus, our immediate ancestor, was the first to emigrate from Africa and to settle in Europe and Asia as well ("Java Man" and "Peking Man" of the old texts). But we then revert to the hypothesis of global impetus and imagine that all Homo erectus populations on all three continents moved together up the ladder of mentality on a wave of predictable and necessary advance, given the adaptive value of intelligence. I call this scenario the "tendency theory" of human evolution. Homo sapiens becomes the anticipated result of an evolutionary tendency pervading all human populations.
In an alternative view, recently given powerful support by reconstructions of our evolutionary tree based on genetic difference among modern groups (Cann, Stoneking, and Wilson, 1987; Gould, 1987b), Homo sapiens arose as an evolutionary item, a definite entity, a small and coherent population that split off from a lineage of ancestors in Africa. I call this view the "entity theory" of human evolution. It carries a cascade of arresting implications: Asian Homo erectus died without issue and does not enter our immediate ancestry (for we evolved from the African populations); Neanderthal people were collateral cousins, perhaps already living in Europe while we emerged in Africa, and also contributing nothing to our immediate genetic heritage. In other words, we are an improbably and fragile entity, fortunately successful after precarious beginnings as a small population in Africa, not the predictable end result of a global tendency. We are a thing, an item of history, not an embodiment of general principles.
The claim would not carry startling implications if we were a repeatable thing -- if, had Homo sapiens failed and succumbed to early extinction as most species do, another population with higher intelligence in the same form was bound to originate. Wouldn't the Neanderthals have taken up the torch if we failed, or wouldn't some other embodiment of mentality at our level have originated without much delay? I don't see why. Our closest ancestors and cousins, Homo erectus, the Neanderthals, and others, possessed mental abilities of a high order, as indicated by their range of tools and other artifacts. But only Homo sapiens shows direct evidence for the kind of abstract reasoning, including numerical and aesthetic modes, that we identify as distinctly human. All indications of ice-age reckoning -- the calendar sticks and counting blades -- belong to Homo sapiens. And all of the ice-age art -- the cave paintings, the Venus figures, the horse-head carvings, the reindeer bas-reliefs -- was done by our species. By evidence now available, Neanderthal knew nothing of representational art.
Run the tape again, and let the tiny twig of Homo sapiens expire in Africa. Other hominids may have stood on the threshold of what we know as human possibilities, but many sensible scenarios would never generate out level of mentality. Run the tape again, and this time Neanderthal perishes in Europe and Homo erectus in Asia (as they did in out world). The sole surviving human stock, Homo erectus in Africa, stumbles along for a while, even prospers, but does not speciate and therefore remains stable. A mutated virus then wipes Homo erectus out, or a change in climate reconverts Africa into an inhospitable forest. One little twig on the mammalian branch, a lineage with interesting possibilities that were never realized, joins the vast majority of species in extinction. So what? Most possibilities are never realized, and who will ever know the difference.
Arguments of this form lead me to the conclusion that biology's most profound insight into human nature, status, and potential lies in the simple phrase, the embodiment of contingency: Homo sapiens is an entity, not a tendency.
By taking this form of argument across all scales of time and extent, and right to the heart of our own evolution, I hope I have convinced you that contingency matters where it counts most. Otherwise, you may view this projected replaying of life's tape as merely a game about alien creatures. You may ask if all my reveries really make any difference. Who cares, in the old spirit of America at its pragmatic best? It is fun to imagine oneself as a sort of divine disc jockey, sitting before the tape machine of time with a library of cassettes labeled "priapulids", "polychaetes", and "primates." But would it really matter if all the replays of the Burgess Shale produced their unrealized opposites -- asn we inhabited a world of wiwaxiids, a sea floor littered with little penis worms, and forests full of phororhacids? We might be shucking sclerites instead of opening shells for our clambakes. Our trophy rooms might vie for the longest Diatryma beak, not the richest lion mane. But what would be fundamentally different?
Everything, I suggest. The divine tape player holds a million scenarios, each perfectly sensible. Little quirks at the outset, occurring for no particular reason, unleash cascades of consequences that make a particular future seem inevitable in retrospect. But the slightest early nudge contacts a different groove, and the history veers into another plausible channel, diverging continually from its original pathway. The end results are so different, the initial perturbation so apparently trivial. If little penis worms ruled the sea, I have no confidence that Austrolopithecus would ever have walked erect on the savannas of Africa. And so, for ourselves, I think we can only exclaim, O brave -- and improbable -- new world, that has such people in it!
Wonderful Life: The Burgess Shale and the Nature of History
by Stephen Jay Gould
VII. The Origin of Homo sapiens
I will not carry out this argument to ridiculous extremes. Even I will admit that t some point in the story of human evolution, circumstances conspired to encourage mentality at our modern level. The usual scenario holds that attainment of upright posture freed the hands for using tools and weapons, and feedback from the bahavioral possibilities thus provided spurred the evolution of a larger brain.
But I believe that most of us labor under a false impression about the pattern of human evolution. We view our rise as a kind of global process encompassing all members of the human lineage, wherever they may have lived. We recognize that Homo erectus, our immediate ancestor, was the first to emigrate from Africa and to settle in Europe and Asia as well ("Java Man" and "Peking Man" of the old texts). But we then revert to the hypothesis of global impetus and imagine that all Homo erectus populations on all three continents moved together up the ladder of mentality on a wave of predictable and necessary advance, given the adaptive value of intelligence. I call this scenario the "tendency theory" of human evolution. Homo sapiens becomes the anticipated result of an evolutionary tendency pervading all human populations.
In an alternative view, recently given powerful support by reconstructions of our evolutionary tree based on genetic difference among modern groups (Cann, Stoneking, and Wilson, 1987; Gould, 1987b), Homo sapiens arose as an evolutionary item, a definite entity, a small and coherent population that split off from a lineage of ancestors in Africa. I call this view the "entity theory" of human evolution. It carries a cascade of arresting implications: Asian Homo erectus died without issue and does not enter our immediate ancestry (for we evolved from the African populations); Neanderthal people were collateral cousins, perhaps already living in Europe while we emerged in Africa, and also contributing nothing to our immediate genetic heritage. In other words, we are an improbably and fragile entity, fortunately successful after precarious beginnings as a small population in Africa, not the predictable end result of a global tendency. We are a thing, an item of history, not an embodiment of general principles.
The claim would not carry startling implications if we were a repeatable thing -- if, had Homo sapiens failed and succumbed to early extinction as most species do, another population with higher intelligence in the same form was bound to originate. Wouldn't the Neanderthals have taken up the torch if we failed, or wouldn't some other embodiment of mentality at our level have originated without much delay? I don't see why. Our closest ancestors and cousins, Homo erectus, the Neanderthals, and others, possessed mental abilities of a high order, as indicated by their range of tools and other artifacts. But only Homo sapiens shows direct evidence for the kind of abstract reasoning, including numerical and aesthetic modes, that we identify as distinctly human. All indications of ice-age reckoning -- the calendar sticks and counting blades -- belong to Homo sapiens. And all of the ice-age art -- the cave paintings, the Venus figures, the horse-head carvings, the reindeer bas-reliefs -- was done by our species. By evidence now available, Neanderthal knew nothing of representational art.
Run the tape again, and let the tiny twig of Homo sapiens expire in Africa. Other hominids may have stood on the threshold of what we know as human possibilities, but many sensible scenarios would never generate out level of mentality. Run the tape again, and this time Neanderthal perishes in Europe and Homo erectus in Asia (as they did in out world). The sole surviving human stock, Homo erectus in Africa, stumbles along for a while, even prospers, but does not speciate and therefore remains stable. A mutated virus then wipes Homo erectus out, or a change in climate reconverts Africa into an inhospitable forest. One little twig on the mammalian branch, a lineage with interesting possibilities that were never realized, joins the vast majority of species in extinction. So what? Most possibilities are never realized, and who will ever know the difference.
Arguments of this form lead me to the conclusion that biology's most profound insight into human nature, status, and potential lies in the simple phrase, the embodiment of contingency: Homo sapiens is an entity, not a tendency.
By taking this form of argument across all scales of time and extent, and right to the heart of our own evolution, I hope I have convinced you that contingency matters where it counts most. Otherwise, you may view this projected replaying of life's tape as merely a game about alien creatures. You may ask if all my reveries really make any difference. Who cares, in the old spirit of America at its pragmatic best? It is fun to imagine oneself as a sort of divine disc jockey, sitting before the tape machine of time with a library of cassettes labeled "priapulids", "polychaetes", and "primates." But would it really matter if all the replays of the Burgess Shale produced their unrealized opposites -- asn we inhabited a world of wiwaxiids, a sea floor littered with little penis worms, and forests full of phororhacids? We might be shucking sclerites instead of opening shells for our clambakes. Our trophy rooms might vie for the longest Diatryma beak, not the richest lion mane. But what would be fundamentally different?
Everything, I suggest. The divine tape player holds a million scenarios, each perfectly sensible. Little quirks at the outset, occurring for no particular reason, unleash cascades of consequences that make a particular future seem inevitable in retrospect. But the slightest early nudge contacts a different groove, and the history veers into another plausible channel, diverging continually from its original pathway. The end results are so different, the initial perturbation so apparently trivial. If little penis worms ruled the sea, I have no confidence that Austrolopithecus would ever have walked erect on the savannas of Africa. And so, for ourselves, I think we can only exclaim, O brave -- and improbable -- new world, that has such people in it!
