Humans today are evolving to be smarter, taller, and to even live longer than their ancestors. According to a recent study published in the journal Nature, the notable shift in height and intelligence throughout evolution may be linked to the genetic diversity of offspring’s parents.

Sexual reproduction is essential to maintain genetic diversity within the human species. It combines the parents’ genetic material, resulting in offspring that possess a unique set of genetic blueprints that increase their chances of surviving and thriving compared to a population with limited genetic variability. This encapsulates Charles Darwin’s theory of natural selection, where individuals with characteristics that increase their probability of survival will have more opportunities to reproduce, according to the University of California, Berkeley’s Understanding Evolution. As a result, their offspring will benefit from the variants, which will spread throughout the population.

In an effort to delve into the positive benefits of “outbreeding,” senior researcher Jim Wilson and his team from the University of Edinburgh in Scotland studied the genetic diversity of genome data with six biomedical traits, ranging from height to cognitive ability. The researchers analyzed more than 100 separate studies carried out around the world, including over 350,000 people living in both rural and urban environments. The findings revealed four traits — height, lung capacity, general cognitive ability, and educational attainment — have increased significantly in correlation with genomes that possessed more genetic diversity.

The genomes of the individuals included those living as far as Finland and East Asia. Non-genetic factors such as differences in upbringing due to socio-economic status were taken into account. However, the researchers still found the level of genetic diversity was still a significant factor affecting the four traits. “There has been speculation ever since Charles Darwin that genetic diversity would be beneficial in terms of evolutionary fitness. We think genetic diversity decreases the chances of inheriting defecting copies of the same gene from both father and mother,” said Peter Joshi, first author of the study, The Independent reported.

The study authors did not find any link between genetic diversity and factors such high blood pressure or cholesterol levels. This is not a surprise considering health problems like diabetes, high blood pressure, and heart disease tend to arise later in life. Meanwhile, human evolution is more focused on the ability to create healthy offspring and have them survive infancy to continue raising them.

Although the effects are relatively small, they do support the notion that increased height and greater intellect are positive components of evolution seen around the world, including Europe, Africa, and Asia. The results place a positive value on genetic diversity, as it promotes the importance of survivability. "This study highlights the power of large-scale genetic analyses to uncover fundamental information about our evolutionary history,” Wilson said in the press release.

Now, when it comes to which groups are genetically diverse, European-American populations are found to be less so and have more potentially harmful genetic variations than African-American populations, according to a 2008 study published in the journal Nature. Researchers point to a population “bottleneck” that may have been involved in the original settlement of Europe, to explain the result. This means that when a certain population begins to shrink over at least one generation, the smaller population leads to reduced genetic variation which can lead to mutations that can affect amino acids, or the building blocks of proteins.

Whether you come from a genetically diverse background or not, in the end even the most common medical ailments that affect society will affect everyone, with genetic diversity having little to no impact.

Sources: Bartz TM, Chasman DI, Concas MP et al. Directional dominance on stature and cognition in diverse human populations. Nature. 2015.

Boyko AR, Bustamante CD, Clark AG et al. Proportionally more deleterious genetic variation in European than in African populations. Nature. 2008.