‘The Handmaid’s Tale’ could give rise to a new humanoid species
With the Emmy winners having recently been announced, many of us have a new list of shows to catch up on with weekend-long binge-watching sessions. One in particular caught our eye: Hulu’s The Handmaid’s Tale, a dystopian story that deftly navigates social issues with a focus on misogyny and societal roles. In the show’s fictional Republic of Gilead, widespread infertility causes reproduction to be limited to a select group of women, whose participation is violently enforced by the oppressive patriarchal government.
It sets the stage for a gripping and disturbing story. And, Helix scientists have observed, it could also lead to some notable genetic phenomena.
Because reproduction in Gilead is limited to a handful of women and a small group of men, this restricted genetic pool would limit the diversity of DNA information being passed on to the next generation—the same genes are being used again and again to give rise to the next generation for an entire society. This situation sets up what is referred to as a population bottleneck, a moment in time where populations of humans (or other species) have suffered a significant reduction in the number of people who can reproduce. Under restrictive conditions and with a low rate of reproduction, bottlenecks can result in reduced genetic diversity and sometimes lead to inbreeding. Historically, this happened most often on geographically remote islands or villages where a catastrophic event significantly decreased the population, leading to inevitable intra-family mating. In The Handmaid’s Tale, a mixture of political and physical limitations squeeze Gilead’s reproductive potential and results in a bottleneck.
A population bottleneck can cause some traits to be lost within a population, while others are disproportionately increased.
Genetically, what would we find in Gilead after a few generations of this effect? In short, we’d expect to see a decrease in genetic diversity and a potential increase in genetic diseases. Given enough time—millions of years—we might even see the evolution of a new species of human.
Disease in the bottleneck
One of the most well-documented outcomes of a population bottleneck is the increased prevalence of genetic diseases, which come about when specific changes in DNA result in a disease.
Most of your genome contains two copies of every gene, one from your mom and one from your dad. One of the benefits to having two copies—also called alleles, pronounced a-lee-uhl-s—is that it provides a backup copy on the off chance that one of them stops working correctly (this system isn’t perfect, though, because there are many instances where the loss of one allele is able to affect gene function). The sequence of each allele is nearly identical; however, there are variants in each allele that, in some cases, can influence your physical traits. For example, one gene may code for your hair color, although different alleles code for black, brown, or red hair. Terms like “dominant” and “recessive” are often used to indicate if a particular allele will be expressed over the other, like the dominant black hair allele which will control hair color in the presence of the recessive red hair allele. Two recessive red hair alleles will result in red hair color because there is no dominant hair color allele present.
Returning to Gilead and the population bottleneck, we anticipate that there will be an increased prevalence of disease after several generations. Assume for a minute that, prior to the formation of Gilead, there are ten people and two of them has a recessive allele that causes a disease when both alleles are present. These alleles would be passed on from generation to generation, but would remain a minority within the population.
After the forming of Gilead, there are considerably fewer people who are able to reproduce and pass on their genes. Let’s say there are two individuals, and one of them happens to carry the disease allele. 25% of their children would have two copies of the allele, and 25% would have a single copy. In this example, because there is a reduced pool of people who are reproducing, the prevalence of the disease allele went from 20% before the bottleneck, up to 75% after the bottleneck. That’s a huge increase. (It’s also possible that an individual with the disease allele doesn’t end up reproducing, which means that particular disease would disappear from the population.)
This is how a disease-causing allele (pink) can be overrepresented in a population following a bottleneck.
A new species?
Assuming Gilead escapes genetic disease and remains isolated for millions of years, we may eventually see the evolution of a new humanoid species. Over generations, our genome accumulates various changes in DNA. Some don’t influence our traits, while others can result in changes to our physical appearance, behavioral tendencies, and health. Charles Darwin’s studies in the Galapagos Islands are a good example of this, where species of finches were isolated on different islands long enough to see signs of evolution. Their isolation lead to the development of different advantageous traits such as beaks shaped for hunting amid the unique plant life of each island. Likewise, if a population of people are isolated in the different cities of Gilead, changes in the DNA can quickly become prevalent within the isolated gene pool. Continual accumulation of these changes can eventually give rise to a population of people who are genetically distinct from what we currently know as “human.” Over tens of millions of years, this fictional world could see the evolution of several new, city-specific species of humans.
There are many nuances that determine the outcome of a bottleneck. In some instances, the effects may hardly be noticeable. But under Gilead’s draconian rules, there could be a much bigger impact. What lies ahead for Gilead is not clear, but history has taught us that a limited genetic pool can have dramatic effects on the health and identity of populations.
The next season of The Handmaid’s Tale can’t come soon enough.
