Cavefish and Zebrafish Embryos
Credit: wellcome images
An important rule of evolution is that species lose adaptations they aren’t using. Cave fish have eyes that do not work because they live in an environment without light. Crocodile icefish blood has lost its hemogloblin because they live in oxygen-rich water where they don’t need the protein to transport oxygen throughout their bodies. Kiwis, chickens, and ostriches have wings but can’t fly. Humans lack the gene to make Vitamin C, forcing us to get our ascorbic acid from dietary sources.
This happens because when a trait isn’t in use, natural selection does not discriminate against mutations that break the trait. For example, when an individual impala is born with a mutation that gives it bad eyes, it gets eaten by a lion, but when a fish in the total darkness of a cave gets bad eyes, they are just as likely to survive as the fish with working vision; in fact, they have a slight advantage for not having to put resources into building and maintaining eyes that provide no advantage.
Crocodile icefish larvae (note the clear blood)
Credit: Unknown Wikipedia User
A question that comes up regularly in popular science media is, Are humans evolving? And the answer depends on what we mean by evolving. If we are talking about the popular public use of the term, which is synonymous with a species getting better (taller, smarter, faster, etc), then the answer is: only in those parts of the world where natural selection is still at work. In Africa, for instance, where famine, disease, and, in some cases, lions are at work there is also natural selection in effect. The inhabitants of famine-stricken areas are being selected for resistance to starvation. Sickle-cell Anemia came out of Africa as an adaptative resistance to Malarial infection by mosquitos; people with the sickle-cell gene survived longer than those without it despite the trait also having a deleterious effect on the carrier.
If we are talking about the scientific definition of evolving, meaning gradual genetic change in a species population over time, then that is occurring in all humans, selected or not; but in First World societies, the change that is occurring is not of the improvement kind, but more of the cavefish kind. Eyeglasses and eye surgery allow people like me to survive. Insulin shots allow type-I diabetes patients and obese people to survive. Immunizations eliminate natural selection for natural immune system resistance to bugs. C-sections have eliminated the need to give birth vaginally. Fertility clinics allow people to reproduce who could not in the past. AIDS drugs allow anyone who is infected to survive rather than select for a natural resistance. Wheelchairs, hearing aids, orthopedic shoes, braces, and a wealth of other medical innovations and modern conveniences have drastically reduced any need for athletic prowess or even most physical abilities in order to survive in modern society.
These are wonderful things. Without them, Vicky and I would not be able to have additional children and our son Sagan might likely have died due to our incompatible blood types (I’m O+, she’s A-), but thanks to a shot of Rh immune-globulin and our pediatrician coaching us, our newborn son overcame his jaundice in his first week of life. Science makes it possible to support 7 billion people on our planet, and keeps most of them in good health and comfort. I am perpetually grateful to scientific progress.
New Zealand Kiwi, Flightless Bird
The complication this creates for us is that every lost survival trait in every human being is a survival trait their children will likely not have. When a couple undergoes fertility treatment, then their children will inherit the need to have fertility treatment. As the medical and engineering sciences discover ever new means for us to survive comfortably despite our flaws, they also perpetuate the inventions that keep so many of us alive.
In other words, as our genes fail us, our memes take over.
H. G. Wells wrote that “Civilization is in a race between education and catastrophe.” He was right in deeper dimensions than he realized. Consider what would happen if we were somehow magically stripped of all our technology so that tomorrow morning the human race were to wake up to a world without modern medicine, agricultural science, textiles, plastics, electricity, and all the other scientific conveniences we take for granted each day. How many of our planet’s 7 billion people would still be alive after a week? We would quickly be reduced to the tribal population levels of just a few brief centuries ago as only the fittest and healthiest survived.
Our ideas are keeping us alive. That means we must work for a society that keeps our ideas alive. Libraries, public schools, laboratories, and institutions of higher learning aren’t just conveniences, they are crucial to our survival, and the more we depend on them the more we will need to depend on them and that’s a good thing.