From: veritasium
Some individuals are consistently more prone to mosquito bites than others, a phenomenon science has shown to be influenced, at least partially, by genetics [00:00:09]. Research, including studies involving genetic testing companies like 23andMe, has identified specific locations on human DNA that correlate with an individual’s attractiveness to mosquitoes [00:00:21].
Mosquito Biology and Attraction Testing
Only female mosquitoes bite, as they require blood proteins to produce their eggs [00:01:20]. The mosquito lifecycle, from egg to adult, takes approximately two weeks [00:01:38]. Adult mosquitoes then seek out vertebrate blood to perpetuate their reproductive cycle [00:01:31].
To study mosquito attraction, scientists use a “Y-tube” apparatus [00:01:49]. In this setup, mosquitoes are released into a holding chamber with a fan creating a draft, leading to two arms of the Y-tube [00:01:54]. One arm contains a “bait” (e.g., a human hand), while the other serves as a control or contains a different bait [00:01:59]. Researchers count how many mosquitoes choose each arm to determine attractiveness [00:03:26].
Evidence for Genetic Influence
The Y-tube test has been instrumental in demonstrating the genetic basis of mosquito attractiveness. A study involving 18 pairs of identical female twins and 19 pairs of fraternal (non-identical) female twins used this test to evaluate individual attractiveness [00:03:19].
Twin Study Findings
Scientists found that mosquito attractiveness was correlated between twins [00:03:36]. This correlation was significantly higher for identical twins, who share more of the same genes, compared to fraternal twins [00:03:50]. This strong correlation in identical twins provides compelling evidence that genetics influence how attractive a person is to mosquitoes [00:03:57].
23andMe Research and Personal Genetic Results
A 2017 study, conducted in collaboration with 23andMe, further explored the genetic links [00:06:05]. Over 16,000 individuals opted into this research, rating their perceived attractiveness to mosquitoes [00:06:15]. Through a genome-wide association study, researchers analyzed the DNA of participants to identify commonalities among those who reported being more attractive to mosquitoes versus those who were not [00:06:21]. This led to the identification of seven specific DNA locations, involving single letter changes, that were associated with varying levels of mosquito attraction [00:06:37].
Analysis of personal genetic results between a frequently bitten individual (Derek) and his less-bitten wife (Raquel) revealed consistent findings [00:05:59]:
- Out of the seven identified genetic locations, they had identical DNA at four [00:06:54].
- At one differing location, Raquel possessed a letter change associated with significantly decreased attractiveness to mosquitoes (a protective effect) [00:07:08].
- At a second differing location, Derek had a letter change associated with decreased attractiveness, though less significant than Raquel’s [00:07:29].
- At the third differing location, Derek had two copies of a variant associated with increased attractiveness to mosquitoes, while Raquel had none [00:07:51].
Overall, their genetic profiles aligned with their anecdotal experiences of mosquito attraction [00:08:07].
Mechanisms of Attraction
The exact mechanisms by which these genetic variations influence mosquito attraction are not fully understood [00:08:25]. However, it is likely related to the volatile chemicals and odors produced by the human body, potentially influenced by the skin’s microbiome (bacteria) [00:08:30].
Mosquitoes are primarily attracted to carbon dioxide emissions [00:08:40]. Factors that increase carbon dioxide output, such as a higher metabolism, recent exercise, larger body size, or pregnancy, can make an individual more attractive [00:08:45]. Other volatile chemicals that attract mosquitoes include lactic acid, acetone, and ammonia [00:08:57]. Conversely, some naturally occurring chemicals, such as octanal, nonanal, decanal, and 6-methyl-5-hepten-2-one, appear to repel mosquitoes or impair their ability to locate a host [00:09:01].
Significance and Evolutionary Aspects
The hereditary nature of mosquito attractiveness is estimated to be comparable to that of height or IQ, indicating a significant genetic role [00:09:19]. Understanding this relationship is crucial given that mosquitoes have the greatest impact on human health of all animals [00:09:30]. They are considered the most dangerous animal globally, with mosquito-borne illnesses leading to over a million deaths annually [00:09:55].
An intriguing evolutionary adaptation highlights this danger: the malaria parasite, once contracted by a human, actually alters the host’s body chemistry to produce an odor that makes them more attractive to mosquitoes [00:10:34]. This facilitates the parasite’s transmission via the mosquito vector, demonstrating the remarkable evolutionary strategies at play [00:10:44].