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Article by: Katherine Lawless

Genetic evolution of human taste found from saliva samples of hunter-gatherers, nomad herders, and farmers in Africa and Asia

2021-06-15

Taste is essential for the interaction of animals with their food and has co-evolved with diet. Humans have peopled a large range of environments and present a wide range of diets, but little is known about the diversity and evolution of human taste perception.”1 

Individual food preferences are highly influenced by our taste perception and taste preference. Taste is one of our five senses that is dedicated to the interaction between living beings and their food. If you travel the world and visit different human cultures, you will notice that humans have high variability in their lifestyles and diets. Little is known about the connection between taste perception and lifestyle, but one research team in Sweden and France wanted to explore this connection by looking at the genetic evolution of human taste 

The science behind human taste...what we know so far. 

 “Taste is listed among the five main values (taste, health, cost, time, and social relationships) in the Food Choice Process Model, which explains the motivations behind food choice decisions. Sensory perceptions, such as taste sensitivity vary widely among individuals that may partly be explained by genetic polymorphisms located in genes involved in taste perception of the five basic taste qualities and the most recently identified fat taste modality.”  2 

There are several types of taste preferences, and humans can perceive 5 different tastes: 

 Taste is perceived on the tongue and is mediated by the chemosensory gustatory system (a sensory system that can detect taste and smell).  

“Taste sensations start by chemical compounds (tastants) binding to taste-receptor-cells (TRCs) assembled in taste buds located within gustatory papillae. TRCs are innervated by nerve fibers that transfer gustatory information to the brain.” 1 

Taste preferences supply useful information to avoid harmful food as well as distinguishing beneficial food fulfilling our nutritional needs. 

Taste differences of hunter-gathers, nomad herders, and farmers of Central Africa and Central Asia.  

So, how did we develop these 5 tastes over time? Why do humans all over the world have a vast variety of taste perception preferences?  

Sjöstrand et al. wanted to explore these questions by looking at the evolution of our diet, lifestyle, and taste perception. To do that, they investigated potential local genetic adaptation to environments, biodiversity, and diet diversity among neighbouring human groups which represent the human past and present, based on their current differing lifestyles and local environments. They tested four populations from Uzbekistan in Central Asia and Cameroon in Africa (shown in the picture below) and collected DNA from saliva samples using Oragene•DNA and taste-recognition tests.

To test the genetics of their taste perception, ABC et al. collected saliva samples using Oragene•DNA from all 4 populations. To measure taste recognition threshold, they chose to measure participants’ taste perceptions for sweet (fructose and sucrose), bitter (quinine), umami (monosodium glutamate), salt (Sodium Chloride), and sour (citric acid). Participants were given a water-based solution that could taste like pure water, sweet, sour, bitter, or umami.

We investigated phenotype differences among populations, conducted GWAS [Genome Wide Association Study] and selection scans for genes and regions potentially involved in taste perception.” 1 

When investigating the phenotype differences among the populations, Sjöstrand et al. also measured the overall sensitivity which averaged all the phenotypes measured in each participant.  

The evolution of taste perception in humans 

Baka Pygmies and Nzime of Cameroon in Africa.  

For overall sensitivity, Bakas were found to be less sensitive than Nzimes. The Nzimes were better at detecting fructose (sweet) and quinine (bitter) than the Baka participants. Forest environments have been suggested to be poor environments (in terms of food energy levels) to survive in without agriculture, so the Baka Pygmies cannot afford to be “picky” about their food in their rainforest environment which is why their taste sensitivity is less overall compared to the Nzime farmers. 1

“Farmer groups like Nzimes, have been more specialized in their food consumption, and in this case, being sensitive to taste might help them to identify spoiled food. An alternative explanation is related to the fact that farming communities are hosts for a multitude of infectious diseases that hunter-gathering communities typically are not immune to [which can explain why Nzimes are more sensitive to bitter taste than the Bakas].1 

When looking at the genomic level, Sjöstrand et al. found that Bakas were enriched with the gene TAS2R42 which is an orphan bitter taste receptor known to overexpress in phantogeusia (a spontaneous metallic, bitter, and salty taste in the mouth). Bakas being less sensitive than Nzimes to quinine (bitter taste) might be linked to this orphan bitter taste receptor.  

Kazakh and Tajik of Uzbekistan in Central Asia. 

For the Kazakh nomad herders and Tajik farmers, the study found no difference in the overall sensitivity but learned that the Kazakhs were significantly better at detecting salt while the Tajiks were better at detecting fructose (sweet). The Kazakh nomad herders are known to have a diet with a higher concentration of salt, as salt is used as a conservative for meat and dairy products.  

When looking at their genes, the team found that the SCNN1B gene was enriched in the Tajik farmers. This gene codes for a beta-subunit of the receptor for salt reception, suggesting that there was an evolutionary change in the ability to perceive salt for lower sensitivity in the Tajik farmers.  

The gene that reflects the difference in fructose (sweet taste) perception is TAS1R2 which codes for a subunit of the heterodimeric receptor for sweet taste.  

“Central Asia is the cradle of several fruit tree domestication events which is likely to have changed the agriculturally based diet of the Tajiks more than the herder diet of the Kazakhs.” 1 

Two other notable genes found were GRM7 and RTP4. GRM7 codes for a receptor involved in conditioned taste aversions (a strong dislike of specific food or foods). RtP4 regulates bitter perception, and both these genes are enriched in Kazakh nomad herders, suggesting that there was an evolutionary change in the Kazakh’s bitter taste perception 

The genetic basis of taste perception shaped by lifestyles. 

Human lifestyles have adapted over thousands of years to new environments, from the lifestyle of a hunter-gatherer to the rise of agriculture, these adaptations and varying lifestyles have created genetic changes in the signaling of taste perceptionSjöstrand et aldemonstrated that even the differing lifestyles of neighbouring populations in the same rainforest climate such as the Bakas and the Nzime can cause a genetic change in your taste perception receptors. As well as the lifestyles of nomad herders in the mountains and farmers in the valley can also cause genetic changes to taste.  

You can access the full publication to learn more, here: Taste perception and lifestyle: insights from phenotype and genome data among Africans and Asians

If you would like to learn more about collecting DNA from saliva or have any questions, you can email us at info@dnagenotek.com or click the picture below to request a free trial of Oragene•DNA collection kits to try.  

Request free trial kits of any DNA Genotek saliva kit

References:

1. Sjöstrand, A.E., Sjödin, P., Hegay, T. et al. Taste perception and lifestyle: insights from phenotype and genome data among Africans and Asians. Eur J Hum Genet 29, 325–337 (2021). https://doi.org/10.1038/s41431-020-00736-2 

2. https://www.frontiersin.org/articles/10.3389/fgene.2019.01272/full

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