Natural selection in a contemporary human population

Abstract

Our aims were to demonstrate that natural selection is operating on contemporary humans, predict future evolutionary change for specific traits with medical significance, and show that for some traits we can make short-term predictions about our future evolution. To do so, we measured the strength of selection, estimated genetic variation and covariation, and predicted the response to selection for women in the Framingham Heart Study, a project of the National Heart, Lung, and Blood Institute and Boston University that began in 1948. We found that natural selection is acting to cause slow, gradual evolutionary change. The descendants of these women are predicted to be on average slightly shorter and stouter, to have lower total cholesterol levels and systolic blood pressure, to have their first child earlier, and to reach menopause later than they would in the absence of evolution. Selection is tending to lengthen the reproductive period at both ends. To better understand and predict such changes, the design of planned large, long-term, multicohort studies should include input from evolutionary biologists.evolutionary rates | heritability | Homo sapiens | medical traits A re contemporary humans experiencing natural selection and evolving in response to it? The answer to that question depends on whom one asks. A long tradition in the medical community (1) holds that natural selection does not operate on contemporary human populations because medicine keeps "alive many who otherwise would have perished" (2). No evolutionary biologist would now agree with that claim, for natural selection works through differential reproductive success rather than simple differential survival, and individuals in contemporary human populations vary in lifetime reproductive success (LRS). Selection operates on any trait that varies and is correlated with LRS, and traits respond to selection with change across generations if they vary genetically. But what traits is selection operating on? Do they include the traits treated by physicians? Previous work (e.g., ref.3) has shown that human life history traits, most significantly age at first reproduction, are currently under selection, but evidence for selection operating on traits of medical importance is scarce. Here, we report estimates of natural selection, and the potential genetic response to selection, in the women of the first two generations of the Framingham Heart Study (FHS) population. The traits we analyzed include traits of medical significance: total cholesterol (TC), systolic blood pressure (SBP), diastolic blood pressure (DBP), and blood glucose (GLU). We had three general aims: first, to correct the still widespread misconception that natural selection is not operating on contemporary humans; second, to make quantitative predictions about future evolutionary change for specific traits with medical significance; and third, to register firmly a point of general cultural interest that follows directly from our first two aims: We are still evolving, and for some traits we c...

Does natural selection favour taller stature among the tallest people on earth?

“…Genetic variation in common single nucleotide polymorphisms measured in unrelated individuals also supports this interpretation [34]. Studies by both biologists and demographers also show a moderate genetic component to fertility traits, such as number of children ever born and the age at first birth, which explains up to 40-50% of the variance in these traits [11,[35][36][37][38]. Such findings were also observed for a historical Dutch population [39].…”

“…Recently, Byars et al [11] showed, on the basis of pedigree data, that natural selection was acting on height among United States women: shorter women had higher lifetime reproductive success than taller women, and their descendants were, on average, predicted to be slightly shorter than they would have been in the absence of selection. Stulp et al [12,13] showed phenotypic associations between stature and reproductive success in the United States, such that shorter women had higher reproductive success than their taller counterparts [12], while average height men experienced greater reproductive success than taller or shorter men ( [13]; findings that were replicated by [14] and [15]).…”

Measuring selection in human populations using the growth rate per generation

“…The rate of evolution is the speed at which the characteristics of a population change. For example, a recent study of a contemporary American population found that if the environment of the 1950s and 1960s continued, evolution would lead to a 1.8% decline in total cholesterol levels over a period of five generations [1]. Similarly, the age at menopause would increase by 0.4 years over the same period.…”

“…I have not found any studies of humans that employ a model that accounts for overlapping generations. Almost all of these studies rely solely on measures of either the quantity of reproduction such as the average children ever born [6,11], or the number of children surviving to a given age [1,5,7,12,15]. Several studies include values of the long-term growth rates [8,9,13,16,17].…”

Sexual attractiveness: a comparative approach of morphological, behavioral neurophysiological signaling in women and nonhuman primate females

“…Howeveu, in line with uecent ueseauch cultuual and genetic evolution seem to closely inteuact in co-evolutionauy puocesses (Richeuson et a., 2010). Natuual selection is still active on changing tuaits in contempouauy humans (Byaus et al, 2009) by effecting adaptations thuough cultuue -gene coevolution, which may act much fasteu as pueviously thought (Field et al, 2016).…”