While working through our evolution unit, I will frequently get questions (sometimes with prompting) about whether or not humans are still evolving. I ask students to think about the four requirements needed for evolution to take place: Variation, Inheritance, Selection, and Time. They will bring up that even though humans share 99.9 percent of the same DNA, there are a number of different phenotypes on which natural selection could act. The concept that those phenotypes are generally inherited from parents to offspring is not usually argued, either. The amount of time required for evolution to occur varies, but for the sake of this argument, we are simply discussing whether under current circumstances, are humans continuing to evolve, so the amount of time is indeterminate, assuming that society continues in a relatively similar state that currently exists (specifically regarding industrialized countries for this argument).
Selection?
That leaves the question of whether there is some sort of selection occurring. Most students cite that the survival rate for humans has been increasing over the last 70 years (crude death rate of 19 per 1000 to about 7.5 per 1000 from 1950 to 2020). The likelihood for an individual to die is low enough that natural selection would have little to no effect on the overall population. Furthermore, crude death rate accounts for all causes of death, including individuals who have already passed their genes on to the next generation. This leads most students to conclude that through vaccination programs and modern medical technology, that there is no selective pressure to act on any specific phenotypes.
This is the point when I usually point out that avoiding being removed from the population is not the only way to be selected for. Many students overlook the role of differential reproduction. Though I don't show it to students, this discussion always brings to mind the (school inappropriate) 2006 film Idiocracy.
WARNING: The video uses profanity and some may find it offensive. A descriptive summary is below.
Essentially, the movie describes that those who are most able and thoughtful regarding the raising of their children, are also the most likely to have a small number of children, or elect to have none. Those who are having large number of children but providing little parental care are practicing r-strategist tactics, but with high survival rates of their young, the allele frequencies of these high success reproducers end up reflecting the general population more.
"We are Borg!"
The question of whether we will eventually "evolve" to incorporate technology into our bodies are no longer a question of "if," but rather "to what extent?" Here, I am using the term "evolve" more generically as it is usually applied to technology rather than biological evolution. From wearing a FitBit to monitor your health to the eSight 3 to help people who are legally blind enhance their vision, the use of wearables is already commonplace. The physical connection and/or implantation of technology is also nothing new. Cochlear implants have helped the deaf recover at least some level of hearing. The ability to control prosthetic limbs with your mind allows entirely new levels of overcoming disabilities. These types of enhancements allow individuals to remove, or at least diminish, obstacles that would otherwise prevent them from living as full of a life. Jason Sosa describes a world where neural implants allow for watching movies as an immersive experience and taking vacations as a Total Recall style of adventure.
My concern with this is the ethics of providing access to these enhancements and how this could open or close doors, in much the same way as in Gattaca. Regarding the question as to whether this would be the next step in human evolution, I would have to say no, at least based on current technology. At the most, current trans-human developments could increase survival rates for those with a disability, but as discussed previously, their survival is already being significantly increased through modern medicine. The other major advantage would be the (potential) increase in access to mates. Many people would find it difficult to date someone who speaks a different language from themselves, so dating someone who is deaf if you do not know American Sign Language might be an obstacle. Use of a cochlear implant might remove that barrier and increase the possibility of reproducing. Since the implants themselves are not heritable, then I do not see the addition of implants as a selective pressure in humans. The presence or absence of implants will more likely be determined by wealth than by genetics. If anything, I see the use of implants changing humanity by broadening the gene pool and allowing a higher diversity of alleles since more people would theoretically be surviving.
What if...?
The main way that I could see the use of implants being the next evolutionary step for humans is if genetic engineering were used to create organic electronics/computers and wetware that could grow as part of us. Then there would be a phenotype that natural selection could act on. Until then, I think that the continued incorporation of technology will continue, but that it doesn't count as biological evolution for humans.
