Evidence for Evolution in Response to Natural Selection in a Contemporary Human Population
The evolution of the contemporary human species is often portrayed as a slow process over many tens of thousands of years that culminated in our now-fixed modern state and form. But research from the University of Edinburgh (U.K.), Université du Québec à Montréal and Université de Sherbrooke in Canada suggests that the genetic mechanisms by which humans evolved continue to operate.
Their 2011 study published in Proceedings of the National Academy of Sciences of the United States of America (PNAS), “Evidence for Evolution in Response to Natural Selection in a Contemporary Human Population,” examined an isolated French-Canadian population that grew from 30 families in the mid-1700s to more than 1,500 people in 1950 to see if human evolution persists in recent generations. Demonstrating continuing evolution, the authors state, may have broad implications for “the accuracy of forecasts, for instance those pertaining to demography or epidemiology, and on which public policies may rely, could well depend on our knowledge of contemporary evolution.”
The study’s findings include:
- Tracking the age of first reproduction (AFR) — what the researchers describe as a “good candidate for an evolving trait in humans” — over the nearly 200-year period indicated that “selection indeed strongly favored women with earlier AFR” and that “women who began reproducing at a younger age also tended to stop at a younger age.”
- The “women giving birth to their first child around the 1930s were about 4 years younger (from 26 to 22 years old) than those who began to reproduce around 1800.”
- Many “factors operated on the island in opposition to socioeconomic or cultural trends operational at a larger scale [and] provide evidence that those changes resulted, at least partly, from a micro-evolutionary response to natural selection on AFR.”
- Controlling for many factors, evidence showed that the “AFR was also highly heritable and genetically correlated to fitness, predicting a microevolutionary change toward earlier reproduction.”
- However, “the advancement of age at maturity, as well as increases in fertility, may reflect plastic responses to improvements in nutritional conditions, such as those observed during the 19th and 20th centuries in Western societies.”
The researchers conclude that the findings support the “idea that humans are still evolving. It also demonstrates that microevolution is detectable over just a few generations in long-lived species.”
Tags: science, parenting
Note to instructor: The suggested assignments are designed for flexibility. They can be used in whole or part and can be adapted to a particular task — for example, the newswriting assignments could be applied to the writing of the headline, the lead, the nut graph or the full story. Material from the assignments could also be combined with other material, for example, in the writing of a background, feature or local-angle story.
Read the study titled “Evidence for Evolution in Response to Natural Selection in a Contemporary Human Population."
- Summarize the study in fewer than 40 words.
- Express the study's key term(s) in language a lay audience can understand.
- Evaluate the study's limitations. (For example: Do the results conflict with those of other reliable studies? Are there weaknesses in the study's data or research design?)
- Write a lead (or headline or nut graph) based on the study.
- Spend 60 minutes exploring the issue by accessing sources of information other than the study. Write a lead (or headline or nut graph) based on the study but informed by the new information. Does the new information significantly change what one would write based on the study alone?
- Interview two sources with a stake in or knowledge of the issue. Be prepared to provide them with a short summary of the study in order to get their response to it. Write a 400-word article about the study incorporating material from the interviews.
- Spend additional time exploring the issue and then write a 1,200-word background article, focusing on major aspects of the issue.