Freethought San Marcos: A column
by LAMAR W. HANKINS
Evolution is science, but most Americans don’t understand it. Only 39% of Americans accept the theory of evolution, while nearly all probably accept the theory of gravity. Most Americans don’t seem to understand that calling a scientific concept a theory doesn’t mean that it is unproved. In fact, the proof for evolution is overwhelming. Evolutionary geneticist Jerry Coyne, in his book (just out in paperback) “Why Evolution Is True,” discusses the known facts that help intellectually honest readers understand that the theory of evolution is indeed proven beyond any reasonable doubt.
While I am not a scientist, I have an understanding of science that most so-called cultural/religious conservatives, like those who make up half of the Texas Board of Education, apparently do not have. Science, by its very nature, is a field of study and inquiry based on proofs and falsification of ideas. It is not necessary to require that biology teachers in Texas schools teach about the “strengths and weaknesses” of evolution, as half of the State Board wants them to do. It is the nature of science to engage subjects based on the truth or falsity of a proposition.
Many people doubt evolution’s validity about the origin of humans because it is impossible to watch human evolution in the span of a lifetime, or even 10,000 lifetimes, but there are still ways to see evolution happening in a short span of time. Take the staphylococcus bacterium that causes infections that plague medical facilities. As Coyne explains, in the early 1940s penicillin was a powerhouse at curing staph infections. But now, 95% of staph infections aren’t affected by penicillin. This resistance to penicillin by staph bacteria is an example of the evolution concept known as natural selection. The evolution of the staph microbe allows it to resist the curative effects of penicillin. As Coyne explains, “mutations occurred in individual bacteria that gave them the ability to destroy the drug (penicillin).” As the bacterium reproduced, only those bacteria that were resistant to penicillin survived, making penicillin ineffective in killing the new generation.
Another commonly known adaptation through natural selection is insects that are resistant to DDT and other pesticides. Gardeners and farmers know, also, about other insects that have adapted to other pesticides and pesky plants that have adapted to herbicides. As Coyne points out, “fungi, worms, and algae have evolved resistance to heavy metals that have polluted their environment,” allowing them to survive these manmade poisons.
We are able to see for ourselves, during our lifetimes, examples of species that made evolutionary changes when faced with natural challenges. To do this, we have to find species that have short generation times. The most famous example in scientific circles is the evolution of the beak in a bird found in the Galapagos Islands. The medium ground finch was studied for several decades during and after a severe drought. The finch normally fed on soft seeds, but the drought left mostly hard seeds as food. During just one generation, through natural selection, the beak and body size increased by 10%. Only those finches that had larger beaks naturally were able to get adequate food (from the larger and harder seeds). Those finches without powerful enough beaks to eat the hard seed died out without reproducing. The larger-beaked finches were able to eat and reproduce offspring with similar large beaks. The ones with larger and more powerful beaks were more successful thriving and reproducing, and predominated through natural selection.
A complete explanation of this evolution story is reported in the book by Jonathan Weiner, “The Beak of the Finch: A Story of Evolution in Our Time.” And a report of 150 cases of observed evolution in a variety of species can be found in “Natural Selection in the Wild“ by biologist John Endler.
Most people, including those who oppose evolution, know about the fossil record. Of course, the fossil record is incomplete, for natural reasons. Only species with certain characteristics can be preserved as fossils. And the conditions must be just right for a species to be preserved in sediment that becomes rock over millions of years.
As Coyne explains, for a fossil to be formed, the dead animal or plant must be in water, sink to the bottom, and be quickly covered by sediment before it decays or is scattered by scavengers. Dead plants and land-dwelling creatures rarely are found on the bottom of water sources like a lake or ocean. Most fossils, then, are marine organisms. To form a fossil, the hard parts of the organism become infiltrated or replaced by dissolved minerals, which becomes compressed into rock by an over-burden of sediment. Soft parts of plants and animals aren’t easily fossilized, so many species don’t become fossils. “[W]orms, jellyfish, bacteria, and fragile creatures like birds are much rarer (as fossils), as are terrestrial species compared to aquatic ones.”
With ten million species now on the earth and an estimated 17 million to 4 billion to have once lived on the earth, we will never find fossils of all species that have ever lived. We have found only 250,000 different fossil species, an inadequate sample for sure, but enough to figure out how the evolution of species proceeded and how major groups split off from one another.
Coyne explains the modern theory of evolution with one long sentence: “Life on earth evolved gradually beginning with one primitive species–perhaps a self-replicating molecule–that lived more than 3.5 billion years ago; it then branched out over time, throwing off many new and diverse species; and the mechanism for most (but not all) of evolutionary change is natural selection.”
In addition to genetic change over time, usually a great deal of time, mutations develop in response to evolutionary pressures. Such change over time is called gradualism. It may take hundreds of thousands of generations, even millions of generations to develop the distinct species we see today. This development occurs through another concept of evolution termed splitting, or speciation. A fourth axiom of evolution is common ancestry, which can be determined through fossil evidence or DNA evidence, which Darwin did not have available over 100 years ago, when he developed his theory.
The fifth part of Darwin’s theory is natural selection, the concept discussed above. Natural selection does not produce the fittest, as is commonly thought, but it produces the fitter–improvements over what came before. And then there are other causes for evolutionary change, such as random changes caused by different families having different numbers of offspring, which has nothing to with the adaptation caused by natural selection. And there are other factors, such as genetic drift, which is a random change in the frequency of genes in an isolated group that is not caused by natural selection.
In 1962, when I began college at a small Methodist-related college, my biology teacher, while offering no apologies for teaching evolution as fact, also suggested that there was no inconsistency between belief in God and evolution. Belief in God is based on faith. Evolution is based on science; that is, it is testable and permits making verifiable predictions. With evolution, it is possible, in Coyne’s words, “to make observations about the real world that either support it or disprove it.” Further, “a good theory makes predictions about what we should find if we look more closely at nature. And if those predictions are met, it gives us more confidence that the theory is true.”
The difference between evolution theory and “intelligent design theory” or “creationism,” as it was originally called, is that evolution is subject to testing and falsification. These faith-based theories are not. No one can test the belief that God created the earth and all of its inhabitants in six days 10,000 years ago. What we know is that the available empirical evidence establishes that organisms have existed on earth for 3.5 billion years.
The first organisms were simple photosynthetic bacteria that were followed two billion years later by more complex organisms. About 600 million years ago, simple multicelled organisms developed (including worms, jellyfish, sponges). Terrestrial plants and tetrapods appeared about 400 million years ago, and then came amphibians, reptiles, birds, mammals, insects millions of years later. Humans appeared on the earth about 7 million years ago. All of the evolution evidence supports the view that humans were and are subject to the same evolutionary processes that affect all other species. Yet, 100 years after publication of “The Origin of Species” and 85 years after the Scopes trial, 61% of Americans do not accept evolution.
Coyne recognizes that something else besides intellectual objection is going on with people unable to accept evolution, though they may not disagree with the science involved: “To these folks, evolution raises such profound questions of purpose, morality, and meaning that they just can’t accept it no matter how much evidence they see. It’s not that we evolved from apes that bothers them so much; it’s the emotional consequences of facing that fact.” Such people worry about what evolution means for morality and values, and for their own humanity. Perhaps such concerns can be addressed elsewhere, but they don’t belong in science class.
Because evolution is science, there is no need to require high school biology teachers to teach alternative, non-scientific theories about the origin of species. The very nature of science makes such a requirement superfluous. Coyne’s 250-page paperback covers well the vast proofs for evolution and is written to appeal to a wide audience. Particularly fascinating is Coyne’s evolutionary explanations for many anomalies in the structure of various species, such as the unnecessarily long vagus nerve in mammals and the prostate gland. And his discussion of vestiges and atavisms, while not new, take on more significance when placed in context. One fact of embryology that predates Darwin’s work is that all vertebrates start out looking like fish embryos. It was Darwin who recognized how evolution explained the significance of this similar appearance of vertebrate embryos–all vertebrates (fish, reptiles, birds, amphibians, and mammals) have a common ancestry.
Coyne wrote the book to help people become familiar with the evidence for evolution, to reduce the extraordinary distrust among Americans about the subject. It remains to be seen if he has succeeded, but at the very least, Coyne has produced a very readable primer about evolution, one that should help Americans gain a better understanding of evolution, as well as science in general.
[Coyne will participate in an interdisciplinary panel discussion at Texas State University on Tuesday, March 23, 12:30 p.m., in Room 132 of the Psychology Building. Participants in the panel include Harvey Ginsberg (Psychology), Peter Hutcheson (Philosophy), Kerrie Lewis (Anthropology), and Rebecca Raphael (Philosophy & Religious Studies). On the evening of March 23, Coyne will speak in the Alkek Teaching Theater at 7 pm. Both events are open to the public.]
© Freethought San Marcos, Lamar W. HankinsEmail | Print