A whole bunch of muscles. In addition to the external ear muscles, Darwin listed an entire catalogue of muscular tissue as candidates for vestigiality. “Rudiments of various muscles have been observed in many parts of the human body; and not a few muscles, which are regularly present in some of the lower animals can occasionally be detected in man in a greatly reduced condition,” he wrote in The Descent of Man. His nominees included the panniculus carnosus, “[r]emnants of this muscle in an efficient state are found in various parts of our bodies; for instance, the muscle on the forehead, by which the eyebrows are raised,” as well as the “[human chest muscles] musculus sternalis or sternalis brutorum found in the proportion of about three per cent. in upward of 600 bodies,” the “muscles pedieux de la main” [small muscles of the hand] and “the superficial muscles on their scalps.” This last, he noted, “offers a good illustration how persistent may be the transmission of an absolutely useless faculty, probably derived from our remote semi-human progenitors; since many monkeys have, and frequently use the power, of largely moving their scalps up and down.”17
You have only to wrinkle your forehead and look into an anatomy text for those chest muscles to realize that, in this case, Darwin appears to have overstepped. But there really is a list of muscles we can do without. First is the subclavis muscle, which runs from the first (top) human rib to the clavicle (collarbone) and would be useful if we still walked on all fours. We don’t, so it isn’t. The palmaris, stretching from elbow to wrist, may once have been useful when we were climbing and swinging through trees. More than 10 percent of us no longer have this one; the ones who do don’t need it, so reconstructive plastic surgeons sometimes harvest it to be used as a replacement for a damaged muscle elsewhere in the body. The plantaris muscle in the back of the calf is useful for primates who use their feet for grasping and holding. That’s not us; about nine in one hundred of us no longer even have this one. Finally there’s the pyramidalis muscle. This one, shaped something like a pyramid and attached to the pubic bone, is useful for marsupials such as kangaroos, wallabies, koalas, Tasmanian devils, wombats, and opossums that have pouches to which their fetal young migrate to develop fully. Repetition may be boring, but once again, this isn’t us. Twenty percent of us don’t even have a pyramidalis muscle, and not a single one of the remaining 80 percent who have it needs it.
Reproductive remnants. “The reproductive system offers various rudimentary structures,” Darwin wrote, “but [h]ere we are not concerned with the vestige of a part which does not belong to the species in an efficient state, but with a part efficient in the one sex, and represented in the other by a mere rudiment. Nevertheless, the occurrence of such rudiments is as difficult to explain, on the belief of the separate creation of each species, as in the foregoing cases.”18 Today we know what Darwin didn’t: very early in our embryonic life, we are neither obviously male nor female, simply works in progress, a situation that changes around the seventh or eighth week of pregnancy. At that point, if we have the male XY gene rather than two female XXs, the SRY gene on the Y chromosome releases a sex determining region Y protein that tells the embryo’s nascent gonads to become testicles rather than ovaries. But tissue does not melt away, so all human beings, male and female, are born with nonfunctioning remnants of the other gender’s reproductive organs. Men have an undeveloped uterus dangling from the prostate gland, and women have the epoophoron, a group of useless sealed tubes near the ovaries that in the male would have been the vas deferens, the tubes through which sperm pass to the ejaculatory duct and then to the urethra and out into the world on their way to a waiting egg.19 Females may also have a leftover remnant of Gartner’s duct, a reminder of the tissue that becomes the epididymis, ductus deferens, ejaculatory duct, and seminal vesicle in the male but in the female may end up stuck in the layer between the uterine ligament and/or the wall of the vagina. And let us not forget the mesonephric tubules, genital ridges that behave like kidneys in the early life of all embryos and then, in a male fetus, shift over to the developing testes, becoming part of the masculine internal genital apparatus.20
ONE UNDISPUTEDLY VESTIGIAL ORGAN
Pheromones are chemical signals that living things, animals and plants, send back and forth to deliver pleasant messages such as, “C’mon over here, handsome,” or scary ones like, “The first one to cross that line gets stomped.”
Your house and garden plants may or may not respond when you talk or sing to them in an attempt encourage their healthy growth, but they definitely “talk” to other organisms via botanical pheromones that play an essential role in a variety of plant life processes. The most important, of course, are the attempt to reproduce and then to survive in a world teeming with predators. To ensure the success of the former, green things emit specific pheromones to attract pollinating insects that scurry from plant to plant, creating the conditions for new ones—plants, that is—wherever they go. As for avoiding predators, Hiroyuki Sekimoto of the Department of Chemical and Biological Sciences at Japan Women’s University (Tokyo) explains that “certain plants emit alarm pheromones when grazed upon, resulting in tannin production in neighboring plants. These tannins make the plants less appetizing for the herbivore.”21
Moving up to the animal kingdom, it is obvious that practically everyone from the tiniest to the largest creatures responds in some ways to olfactory messages. Insects get theirs, including the messages from pheromones, through their antennae. More complex creatures may get theirs through olfactory receptors located on the vomeronasal organ (VMO), two structures pinned to the lining of the nose or the roof of the mouth and found in a wide variety of animals, from snakes to dogs to us. Millennia ago, when we stood up on two legs rather than continuing to move on four limbs, we no longer sniffed the ground for information. Instead, our sense of sight replaced our sense of smell as our most important translator of data from the world. Vision allows us to assess and react to the images we perceive before us, differentiating not simply between light and dark, solid and liquid, but also most important, to an us and them divided by more complicated factors than, say, the simple odor of a friend or foe.
To do this requires what may be our most complicated neural signals and responses, more so than any of our other senses, certainly more than the sense of smell. So it is likely that our newly acute vision made our VMO pretty much unnecessary and eventually led to its becoming much smaller than the VMO for other mammals. A dog’s VMO, for example, may take up as much as sixty square inches, all covered with tiny hairs (cilia) and holding as many as three hundred million olfactory receptors along with nerves that send fibers from the VMO receptor sites straight to the brain, which decodes the odor messages. By comparison, our human VMO covers only one square inch with as few as 5 million or so receptors, and we have no nose-to-brain nerve connectors. In 2004, researchers at the Max Planck Institute for Evolutionary Anthropology in Germany and the Weizmann Institute in Israel labeled about 60 percent of the genes in the human VMO (and 30 percent of those in the nonhuman primate VMO) as pseudogenes. To paraphrase neuroscientist Michael Meredith of Florida State University in Tallahassee, that means that the genes in the human VMO receptors are pretty much dead as dodos, defective pieces of DNA that look like genes, but do not transmit messages.22, 23
8
Future Man
“Man may be excused for feeling some pride at having risen, though not through his own exertions, to the very summit of the organic scale; and the fact of his having thus risen, instead of having been aboriginally placed there, may give him hopes for a still higher destiny in the distant future.”
Charles Darwin, The Descent of Man
YES. NO. MAYBE.
Good news or bad, most of us can live with certainty. It’s maybe that drives us to distraction, so from the beginning of time, humans have been attempting to predict the future. The Greeks had their Oracle at Delphi. At the age of 92, when he was a prisoner on Patmos, an island in the Aegean Sea where Rome stashed its religious and
political dissidents, the Christian apostle John wrote a Book of Revelation to predict how it would all end. Michel de Nostredame published the first edition of Les Propheties in 1555; it’s still in print, a record every author would give his or her pen, pencil, typewriter, computer, printer, and iPhone to achieve. And just to prove that the belief in magic dies hard, even now most 21st-century American newspapers carry a daily astrology column, and at least one 20th-century American President brought an astrologer or two with him in into the White House.
Of course, Charles Darwin was most curious about our past, not our future. Today, the challenge for those who followed him have struggled to correct by guessing what humans will look and act like centuries from now. As they and we contemplate our future selves, there are two possibilities: one, we will continue to evolve, and two, we won’t. In other words, in terms of Darwinian progression, we are either at the end of the beginning or the beginning of the end.
THE END OF EVOLUTION
There are two types of evolution: the Darwinian model and the kind of evolution we make for ourselves. Darwin’s view of our ascent from lesser animals depends on the all-important concept of natural selection, which depends in turn on a number of accidents starting with genetic mutation and the isolation of communities that creates a situation in which the mutation can be passed on. In this scenario, the new trait becomes imbedded in the recipients’ DNA to be passed on again and again and so on.
Neither of these conditions—natural selection and isolation—is as important to us as they were to our ancestors. For example, suppose that around the year 1590, a Russian baby boy was born with a mutation that made it possible for him to survive in very cold weather on a very limited diet. His mutated gene(s) would enable him to survive when food was scarce and the weather turned frigid. In short, his body was perfectly made for the period from 1600 to 1603, when worldwide record cold winter and worldwide crop failures followed a major explosive eruption of the Peruvian volcano Huaynaputina (“new volcano”). Like the disastrous Krakatoa eruption nearly 300 years later, Huaynaputina sent enough dust into the air to block sunlight, lower temperatures, and disrupt the earth’s agriculture.1, 2
For all we know, just such a boy was indeed born. And because one man can father many children, he might have passed his new cold-and-famine-resistant genes on to the next generation and the next and the next and so on. Theoretically at least, he might have created a whole population of people who live happily with cold and may for at least a while stay healthy on a diet that would not work for the rest of us.
But today, says Steve Jones, professor of genetics at Galton laboratory of University College London, that kind of genetic accident matters much less because “[i]n a modern world of central heating and plenty of food, the same mutation is far less likely to give a child any advantage.”3 Besides, says anthropologist Ian Tattersall of New York’s American Museum of Natural History, “Everything we know about evolutionary change suggests that genetic innovations are only likely to become fixed in small, isolated populations,” and in the 21st century, we are all over the place and so incredibly mobile that “the fixation of any meaningful evolutionary novelties in the human population is highly improbable.”4
University of Wisconsin (Madison) anthropologist John Hawks agrees. There would have to be some truly “major new isolating mechanism” to push human evolution drastically forward. Isolation alone won’t do it. After all, despite up to 30,000 years of partial isolation among populations in places such as Australia and Papua New Guinea, humans have remained identifiably human. A second example is that of the people who walked over the ice bridge known as “Beringia,” across the Bering Strait from Russia to North America, about 14,000 years ago. DNA studies suggest that they populated what is now Canada and the United States.5 But as Hawks notes, “when new people [Europeans] showed up 500 years ago, they [the original pedestrians] were still the same species.” On the other hand, if in the far distant future, “we have spacefaring people who went on one-way voyages to distant stars, that,” he says, “might be enough to trigger speciation.”6 Unless that happens, the best bet on our future selves may come from London’s Jones, who explains that our genetic “history is made in bed, but nowadays the beds are getting closer together. We are mixing into a global mass, and the future is brown. So, if you are worried about what Utopia is going to be like, don’t. At least in the developed world, and at least for the time being, you are living in it now.”7
Naturally, scientists being human and humans being contentious, others disagree.
THE NEXT EVOLUTION
Menno Schilthuizen is an evolutionary biologist and ecologist at the Naturalis Biodiversity Center in Leiden (The Netherlands) and a professor of character evolution and biodiversity at Leiden University. “With urban environments expanding all over the world, wildlife and biologists alike are starting to treat the city as a true ecosystem… as entirely novel forms of life are evolving right under our noses.” His first example is the blackbird he saw nesting in a plant on a friend’s balcony. Early on, these birds that had lived in forests and woodlands began to move into cities, where the temperature is higher, the air is dirtier, and the noise is noisier. Like Darwin’s finches, once isolated in a new environment, the city, they evolved. The new blackbirds, Schilthuizen notes, “have stockier bills, sing at a higher pitch (high enough to be heard over the din of traffic), are less likely to migrate (in cities there’s food and warmth year-round), and have less nervous personalities. For many of these differences, genes are responsible. The birds’ DNA, after 200 years or less of adaptation, has diverged from that of their rural ancestors.”8 Similar things seem to be happening elsewhere in the world. In New York parks, Fordham University biologist Jason Munshi-South discovered that white-footed mice, now found in small areas of forested parkland, are equipped with new genes that make it possible for them to tolerate the heavy metals in contaminated city soils or with a stepped-up immune system to ward off illnesses that spread more easily among individuals in crowded populations. Mother Nature, it seems, continues to protect her children.9
She may have simple changes in mind for us, as well. In October 2009, a team of researchers from Yale wrote in Proceedings of the National Academy of Sciences that for various biological reasons, short, plump women are likely to become pregnant more often than tall thin ones. As a result, because these women pass their physical traits on to their offspring, we are likely to have more short, plump women in the future. In other words, the authors said, natural selection is alive and kicking.10
And Nature is likely to continue to play its usual role, tossing challenges in our evolutionary path. As University of New Mexico evolutionary psychologist Geoffrey Miller notes, our modern mobile civilization faces us with “a global pathogen pool of viruses and bacteria that get spread around by air travel to every corner of the Earth, and that’s going to increase…. We’re going to get a lot more epidemics [and] that will increase the importance of the genetic immune system in human survival.” The result, Miller concludes, will be humans with stronger immune systems.11
And if Nature takes a holiday, man (and woman) may have some proposals of his (and her) own.
MAN IMPROVING MAN
For a long time, practically since the Pilgrims stepped off the Mayflower onto Plymouth Rock, Americans stood higher than everyone else as successive waves of immigrants produced successive waves of first-generation better-fed, healthier, and taller children. In 1850, for example, Americans were on average nearly two inches taller than the British from whom they had won their independence, and after that, for a long time, they had about two and a half inches on people from every European country.
Early in the 20th century, Americans simply assumed that this would continue and that every generation would grow taller and live longer, but that didn’t happen. The original increase in height and health rested on the simple fact that children of immigrants ate better over here than their parents had in the Old Country a
nd thus grew stronger and taller. While about 80 percent of our height depends on our genes, the rest can be the result of environmental factors such as clean, nutritious food and a medical system that protects growing children. As the New Yorker’s Burkhard Bilger succinctly put it, “Height variations within a population are largely genetic, but height variations between populations are mostly environmental, anthropometric history suggests. If Joe is taller than Jack, it’s probably because his parents are taller. But if the average Norwegian is taller than the average Nigerian it’s because Norwegians live healthier lives.”12, 13
In short, as other countries caught up to American food and medicine, the picture changed. Today, the Dutch are the tallest among us, averaging 6’ for men and 5’7” for women; the average American man is 5’9” and the average American woman, 5’4.” It is suggested that one possible reason for the change in the United States averages is that different groups of people have different body types, and modern immigration has brought in people from countries where men and woman are simply genetically at the shorter end of the bell curve.
As for living longer, healthy people not only grow taller and stronger, they are also likely to make it to an older age. At the turn of the 20th century, in 1900, as many as three of every ten American infants died before reaching their first birthday. Over the next one hundred years, the environment for infants—in fact for all of us—grew significantly healthier due to advances such as:
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