Review: How Asia's Super Divers Evolved for a Life At Sea

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This article, presented in the Atlantic, briefly reviews the latest work of Melissa Ilardo, a scientist for the University of Copenhagen’s Center for GeoGenetics. Ed Yong, the article’s author, states that Ilardo may have discovered distinctive genetic adaptations in humans that spend a good deal of time underwater. According to the article, the Bajau people, who dwell near the coast in Indonesia and who dive for much of their food, have developed larger spleens to help them dive longer. Given this remarkable claim, skeptical observers may notice some details about this article and wonder if it is objective; despite these concerns, the data presented makes this source look very credible.

Skeptics may see the silly-looking term “Super Divers” in the title of this article and immediately find themselves alerted for other signs of bias and subjectivity. Some signs of bias do appear near the article’s end. As noted in the article, Melisa Ilardo seems to have a strong emotional connection to the Bajau, the population she is studying. She states, “I think it’s wrong to take the [genetic] samples and disappear forever…I hope [the Bajau] get something out of it…. I want to spread a positive message about this population…I have a Bajau mom and dad who adopted me.” Some might wonder if such a strong emotional connection as an adopted family might bias Ilardo’s results. Could her desire to show the Bajau people in a favorable light bias the results of her genetic tests?

While these signs do indicate bias, the data presented suggests that this bias does not destroy the article’s credibility. The article notes certain objective checks that make the data look stronger: 

Ilardo measured the spleen size of 59 villagers with an ultrasound machine (Yong). This method gives Ilardo real, objective data, not just hearsay, anecdotes, or case studies. 

Ilardo compared the spleen sizes of villagers who dive and those who don’t and found that all of the villagers have larger spleens (Yong). This comparison supports the claim that the trait for large spleens is passed between families genetically, and is not only the result of frequent diving, the way a certain group's muscles might get bigger if they lifted weights. 

Ilardo tested not only the Bajau, but also a nearby group of people who don’t dive and who don’t intermarry with the Bajau. The spleens of the Bajau were 50% bigger than the spleens of the neighboring group (Yong). This is a significant difference in spleen size. It also helps that there are two correlating factors, the difference in dive time and the genetic isolation of the two groups. If both groups were divers, the difference in spleen size could easily be attributed to some other factor.

Despite its somewhat outlandish title and the emotional links between Melisa Ilardo and the Bajau people, this article shows enough objective factors in place to suggest that Ilardo’s findings are significant. This article is, for the most part, a very credible source.

Works Cited

Yong, Ed. “How Asia's Super Divers Evolved for a Life At Sea: Scientists are starting to uncover thegenetic basis of the Bajau people’s incredible breath-holding abilities.” theAtlantic, https://www.theatlantic.com/science/archive/2018/04/bajau-sea-nomads-diving-evolution-spleen/558359/. Accessed 17 Sep. 2019.