Saturday, March 27, 2010

After Reproductive Age

Jerry Coyne sadly reiterates how humans have acquired traits via evolution that encourage reproduction yet may produce a bad effect on us after reproductive age. This is why we "('senesce') as we reach old age." (120) This explains why people that are genetically prone to have heart disease, for instance, are still able to pass on their genes just as well as others. Heart diseases generally only prove fatal in the late middle ages, after reproductive age has passed. Because we have the medicine to postpone many of our diseases until after reproductive age, is it reasonable to assume that we are losing our tough, evolutionary edge? Why or why not? Also, what other traits help us "sow [our] wild oats when young" while proving to be annoyances later on, besides Coyne's examples of wrinkles and an enlarged prostate? (121)


  1. Even though heart disease is one such example of an ailment which affects humans after reproductive age, passing on genes is not a problem because “it is reproduction, not survival, that determines which genes make it to the next generation and cause evolution” (Coyne 120) because “passing on a gene requires that you first survive to the age at which you can have offspring” (Coyne 120). In essence, “fitness” is determined then not by how fit one is to the environment over the span of their lifetime, but rather the span from birth to reproduction! Unsurprisingly, this is the reason why undesirable traits like susceptibility to prostate cancer and, as another example, type-II adult onset diabetes, are not “phased out” by evolutionary means. Take former Cubs third baseman Ron Santo for example. In his prime (in our case, peak reproductive age), Santo hit .313 in 1964, received 5 Golden Gloves, and often topped 100 RBI’s in subsequent seasons. A successful baseball player, and a picture of health. However, as time went on, he developed diabetes, which necessitated amputation of one of his legs and lowered his quality of life substantially. In the wild, even though this may sound a bit funny, Santo would have reproduced by his early 20’s due to his great health at the time and great “fit” for survival until reproductive age, but would have surely died afterwards as the diabetes would have killed him. Even though he is no longer that same picture of health now, his genes have still been passed on.

    This brings us to the other point of “losing our evolutionary edge” by postponing illness. My view is that we are not losing our evolutionary edge, but rather extending would-be “reproducers” lives beyond the points which they would originally be terminated in life. Going back to Ron Santo, his diabetes developed full-scale in his late 20’s, yet is still living at 70 today due to modern medicine. He had kids in today’s world, and still would have even if doctors didn’t exist.

    Another such example of this would be certain chronic diseases. As stated by an Autoimmunity research foundation article on chronic disease, certain diseases “known to be genetic in origin offer some characteristic which confers a reproductive edge” and thus continue to survive because of their onset after reproductive age. Sure, some diseases occur before, but that is besides the point as a great number occur afterwards. This just goes to show that many of these diseases and unwanted traits can still be passed on even in non-medically-controlled situations due to the onset after reproductive age. So, we are not losing our evolutionary edge, merely extending people’s lives beyond their original endpoints before medicine.

    Page 120 of the Book

  2. According to Jerry Coyne on page 120, "An adaptation must evolve by increasing the reproductive output of its possessor." This means as long as a species has the selective advantage it needs to survive and reproduce then evolution has done its job. Genes that are disadvantageous after reproductive age are still going to be in the gene pool because they affect the organism when it's already too late. For this reason, I believe that medicine is disrupting our "evolutionary edge," but on a micro-level.

    Unlike organisms such as algae or sharks, humans have only been around for a small fraction of life on Earth. Given this small increment of time, humans are just in the beginning chapters of their evolutionary hi"story;" the type of evolution we are witnessing today is micro-evolution. Natural selection is a much slower process than artificial selection, which is clearly visible in the evolution of dogs as Coyne points out on page 126 of his novel: "All those breeds have been selected in less than ten thousand years, only 0.1 percent of the time that it took wild dog species to diversify from their common ancestor in nature." WIth the advanced technology and medicinal breakthroughs of this day and age, we can prolong diseases until later in life and virtually be promoting individuals to receive traits that can lead to their death later in life. This is not supported by natural selection. Don't get me wrong, I believe everyone should be able to live as long as possible, but when all is said and done we are reversing the effects of evolution (micro-level).

    Along with medicine, it is also possible for couples to essentially choose what genes their child will receive through genetic engineering. This is a completely different outlook on the way humans can alter their evolutionary pathways through the uses of laboratories. According to, genetic engineering is a "two-part series." First of all, it's basically the process of manipulating our genes in such a way as to make our bodies better. This alteration of a genome could take place in the sperm and egg cells, which "Is known as germline gene therapy and would alter the traits that a child is born with." The other way to change our genome is to "swap our bad genes for good ones- in cells other than the sex cells." This is known as "Somatic cell gene therapy." This treatment can displace a defective gene with a properly functioning gene in terms of artificial selection by humans. This can forever change a family's genetics and put an end to devastating "bad genes" that the family previously carried and passed on before hand. If that is not making us lose our "tough, evolutionary history" then I don't know what it is.

    All in all, science and medicine are similar to highway exits because they give humans the option on which direction they can go in their lives. They let us cure our diseases and live longer and pass on our genes to our kids despite the fact that some of us according to evolutionary theory should not be able to do.

  3. The evolution of humans is going to be affected by technology, medicine, and communication. Whether it has affected our evolutionary edge is a debatable question. The example of heart disease has little to no affect on our evolution. People live to their reproductive age and are able to reproduce and pass on their genes. As we have been told by Mr. Erdmann several times, the goal of all animals is to survive and reproduce, so things like heart disease that only affect us after our reproductive age, reguardless of medicines, doesn’t affect our evolutionary edge at all. Diseases that we have been able to postpone until after reproductive age also have no affect on our evolution. Because we have been able to make these diseases non influential in reproduction and the passing on of genes, they have become insignificant to our evolutionary edge, what they do after reproduction age doesn’t matter in the theory of evolution. So medicines haven’t hurt our evolutionary edge, only made many diseases unimportant in terms of our evolution. Other examples of traits that appear later in our life would be shrinking, graying of hair, balding , and a slower metabolism. These are because as we get older, we aren’t able to function as well, so we start to show signs of old age.