Why Evolution Is True (39 page)

Deriving your spirituality from science also means accepting an attendant sense of humility before the universe and the likelihood that we’ll never have all the answers. The physicist Richard Feynman was one of these stalwarts:

But it’s too much to expect everyone to feel like that, or to assume that
The Origin of Species
can supplant the Bible. Only relatively few people can find abiding consolation and sustenance in the wonders of nature; even fewer are granted the privilege of adding to those wonders through their own research. The British novelist Ian McEwan laments the failure of sci- ence to replace conventional religion:

I certainly make no claim to be the Milton of Darwinism. But I can at least try to dispel the misconceptions that frighten people away from evolution and from the amazing derivation of life’s staggering diversity from a single naked replicating molecule. The biggest of these misconceptions is that accepting evolution will somehow sunder our society, wreck our morality, impel us to behave like beasts, and spawn a new generation of Hitlers and Stalins.

That just won’t happen, as we know from the many European countries whose residents wholly embrace evolution yet manage to remain civilized. Evolution is neither moral nor immoral. It just is, and we make of it what we will. I have tried to show that two things we
can
make of it are that it’s simple and it’s marvelous. And far from constricting our actions, the study of evolution can liberate our minds. Human beings may be only one small twig on the vast branching tree of evolution, but we’re a very special animal. As natural selection forged our brains, it opened up for us whole new worlds. We have learned how to improve our lives immeasurably over those of our ancestors, who were plagued with disease, discomfort, and a constant search for food. We can fly above the tallest mountains, dive deep below the sea, and even travel to other planets. We make symphonies, poems, and books to fulfill our aesthetic passions and emotional needs. No other species has accomplished anything remotely similar.

But there is something even more wondrous. We are the one creature to whom natural selection has bequeathed a brain complex enough to comprehend the laws that govern the universe. And we should be proud that we are the only species that has figured out how we came to be.

Notes

1
The modern theory of evolution is still called “Darwinism,” despite having gone well beyond what Darwin first proposed (he knew nothing, for example, about DNA or mutations). This kind of eponymy is unusual in science: we don’t call classical physics “Newtonism” or relativity “Einsteinism.” Yet Darwin was so correct, and accomplished so much in
The Origin,
that for many people evolutionary biology has become synonymous with his name. I’ll sometimes use the term “Darwinism” throughout this book, but keep in mind that what I mean is “modern evolutionary theory.”

2
Unlike matchbooks, human languages
do
fall into a nested hierarchy, with some (like English and German) resembling each other far more than they do others (e.g., Chinese). You can, in fact, construct an evolutionary tree of languages based on the similarity of words and grammar. The reason languages can be so arranged is because they underwent their own form of evolution, changing gradually through time and diverging as people moved to new regions and lost contact with one another. Like species, languages have speciation and common ancestry. It was Darwin who first noticed this analogy.

3
Wooly mammoths died out about ten thousand years ago, probably hunted to extinction by our ancestors. At least one ancient specimen was so well preserved by freezing that in 1951 it furnished meat for an Explorer’s Club dinner in New York.

4
It’s likely that ancestral mammals retained their adult testes in the abdomen (some mammals, like the platypus and elephant, still do), which makes us ask why evolution favored the movement of testes into an easily injured position outside the body. We don’t yet know the answer, but a clue is that the enzymes involved in making sperm simply don’t function well at core body temperature (that’s why doctors tell potential fathers to avoid warm baths before sex). It’s possible that as warm-bloodedness evolved in mammals, the testes of some groups were forced to descend to remain cool. But perhaps external testes evolved for other reasons, and the enzymes involved in making sperm simply lost their ability to function at higher temperatures.

5
Opponents of evolution often claim that the theory of evolution must also explain how life originated, and that Darwinism fails because we don’t yet have the answer. This objection is misguided. Evolutionary theory deals only with what happens
after
life (which I’ll define as self-reproducing organisms or molecules) came into being. The origin of life itself is the remit not of evolutionary biology, but of abiogenesis, a scientific field that encompasses chemistry, geology, and molecular biology. Because this field is in its infancy, and has yet given few answers, I’ve omitted from this book any discussion of how life on earth began. For an overview of the many competing theories, see Robert Hazen’s
Gen*e*sis: The Scientific Quest for Life’s Origin.

6
Note that for the first half of life’s history the only species were bacteria. Complex multicellular organisms don’t show up until the last 15 percent of the history of life. To see an evolutionary timeline in true scale, showing how recently many familiar forms arose, go to
http://andabien.com/html/evolution-timeline.htm
, and keep scrolling.

7
Creationists often use the biblical concept of “kinds” to refer to those groups that were specially created (see Genesis 1:12-25), but within which some evolution is allowed. Explaining “kinds,” one creationist Web site claims, “For example, there may be many species of doves, but they are all still doves. Therefore, doves would be a ‘kind’ of animal (bird, actually).” Thus, microevolution is allowed within “kinds,” but macroevolution
between
kinds could not, and did not, occur. In other words, members of a kind have a common ancestor; members of different kinds do not. The problem is that creationists give no criterion for identifying “kinds” (do they correspond to the biological genus? The family? Are all flies members of one kind, or of different kinds?), so we cannot judge what they see as the limits to evolutionary change. But creationists all agree on one thing:
Homo sapiens
is a “kind” by itself, and therefore must have been created. Yet there is nothing in either the theory or data from evolution implying that evolutionary change could be limited: as far as we can see, macroevolution is simply microevolution extended over a long period of time. (See
http://www.clarifyingchristianity.com/creation.shtml
and
http://www.nwcreation.net/biblicalkinds.html
for the creationist view of “kinds,” and .
http://www.geocities.com/CapeCanaveral/Hangar/2437/kinds.htm
for a rebuttal.)

8
Paleontologists now think that all theropods—and that includes the famous
Tyrannosaurus rex
—were covered with some form of feathers. These aren’t usually shown in museum reconstructions, or in movies like
Jurassic Park.
It wouldn’t bolster the fearsome reputation of
T. rex
to show it covered with fluff!

9
For an engrossing description of how “Dave,” the first
Sinornithosaurus
specimen, was found and prepared, see
http://www.amnh.org/learn/pd/dinos/markmeetsdave.html
.

10
NOVA
made a brilliant television program documenting the finding of
Microraptor gui
and the subsequent controversy about whether it flew. “The Four-Winged Dinosaur” can be seen online at
http://www.pbs.org/wgbh/nova/microraptor/program.html
.

11
In a stunning recent achievement, scientists have managed to obtain fragments of the protein collagen from a 68 million-year-old fossil of
T. rex,
and determined the amino acid sequence of these fragments. The analysis shows that
T. rex
is more closely related to living birds (chickens and ostriches) than to any other living vertebrates. The pattern confirms what scientists have long suspected: all the dinosaurs went extinct except for the one lineage that gave rise to birds. Increasingly, biologists recognize that birds are simply highly modified dinosaurs. Indeed, birds are often
classified
as dinosaurs.

12
The sequence of whale DNA and protein shows that among mammals they are most closely related to the artiodactyls, a finding completely consistent with the fossil evidence.

13
To see a water chevrotain taking to the water to escape an eagle, go to
http://www.youtube.com/watch?v=13GQbT2ljxs
.

14
The paper was published, however, and showed that despite their different styles of running, ostriches and horses use similar amounts of energy to cover the same distance: M. A. Fedak and H. J. Seeherman. 1981. A reappraisal of the energetics of locomotion shows identical costs in bipeds and quadrupeds including the ostrich and the horse.
Nature
282:713-716.

15
This video shows how wings are used in mating:
http://revver.com/video/213669/masai-ostrich-mating/
.

16
Whales, which lack external ears, also have nonfunctional ear muscles (and sometimes tiny, useless ear openings) inherited from their land-mammal ancestors.

17
Pseudogenes are, to my knowledge, never resurrected. Once a gene experiences a mutation that inactivates it, it quickly accumulates others that further degrade the information for making its protein. The chance of all those mutations reversing themselves to reawaken the gene is nearly zero.

18
Predictably, marine mammals that spend part of their time on land, like sea lions, have more active OR genes than do whales or dolphins, presumably because they still need to detect airborne odors.

19
Creationists often cite Haeckel’s “fudged” drawings as a tool for attacking evolution in general: evolutionists, they claim, will distort the facts to support a misguided Darwinism. But the Haeckel story is not so simple. Haeckel may not have been guilty of malfeasance, but only of sloppiness: his “fraud” consisted solely of illustrating three different embryos using the same woodcut. When called to account, he admitted the error and corrected it. There’s simply no evidence that he consciously distorted the appearance of embryos to make them look more similar than they were. R. J. Richards (2008, chapter 8) tells the full story.

20
Our ancestry has left us with many other physical woes. Hemorrhoids, bad backs, hiccups, and inflamed appendixes—all of these conditions are the legacy of our evolution. Neil Shubin describes these and many others in his book
Your Inner Fish.

21
It also inspired William Cowper’s poem “The Solitude of Alexander Selkirk,” with its famous first line:

22
For an animation of continental drift over the last 150 million years, see
http://mulinet6.li.mahidol.ac.th/cd-rom/cd-rom0309t/Evolution_files/platereconanim.gif
. More comprehensive animations over earth’s entire history are at
http://www.scotese.com/
.

23
This phrase, surely Tennyson’s most famous, comes from his poem “In Memoriam A.H.H.” (1850):

24
A graphic video of Japanese hornets preying on introduced honeybees, and being cooked to death by defending Japanese honeybees, can be seen at
http://www.youtube.com/watch?v=DcZCttPGyJ0
. Scientists have recently found yet another way that bees kill hornets—through suffocation. In Cyprus, local honeybees also form a ball around intruding hornets. Wasps breathe by expanding and contracting their abdomen, pumping air into their bodies through tiny passages. The tight bee-ball prevents the wasps from moving their abdomens, depriving them of air.

25
Carl Zimmer’s
Parasite Rex
recounts many other fascinating (and horrifying) ways that parasites have evolved to manipulate their hosts.

26
There’s another aspect of this story that is almost as amazing: the ants, which spend a lot of time in trees, have evolved the ability to glide. When they fall off a branch, they can maneuver in the air so that, instead of landing on the hostile forest floor, they swoop back to the safety of the tree trunk. It’s not yet known how a falling ant can control the direction of its glide, but you can see videos of this remarkable behavior at
http://www.canopyants.com/video1.html
.

27
Creationists sometimes cite this tongue as an example of a trait that could not have evolved, since the intermediate stages of evolution from short to long tongues were supposedly maladaptive. This assertion is baseless. For a description of the long tongue and how it probably evolved by natural selection, see
http://www.talkorigins.org/faqs/woodpecker/woodpecker.html
.