Study finds an unexpected link between farming and immune system evolution

New study questions expected link between farming and overwhelming immune system evolution
Batwa children play on the outskirts of the Bwindi Impenetrable Forest in Uganda. The immune systems of adult Batwa hunter-gatherers showed more signs of positive natural selection, in particular among genes involved in the response to viruses, when compared to those of their farming neighbors in a new study. Credit: University of Chicago Medical Center

Researchers have long theorized that cultural shifts thousands of years ago from hunting and gathering to agriculture and living in permanent settlements spurred an increase in diseases like smallpox and measles. Compared to hunter-gatherers, farmers stayed put, living close to one another and their animals.

This, it's hypothesized, made it easier for viruses and bacteria to spread among humans or from animals to people. Consequently, it might be expected that the immune systems of people from these farming populations would show more signs of positive natural selection through adaptation to these pathogen conditions.

A new study published in Nature Ecology & Evolution by University of Chicago Medicine genetic researcher Luis Barreiro, Ph.D., shows that the opposite is true when comparing farmers and hunter-gatherers in southwest Uganda. Instead, the immune systems of hunter-gatherers showed more signs of positive natural selection, in particular among genes involved in the response to viruses.

"It's the complete opposite of what we expected based on the long-standing hypothesis that the advent of agriculture increased selective pressures imposed by pathogens in ," said Barreiro, the study's senior author and an associate professor in the university's section of genetic medicine.

Researchers studied the blood of the Batwa, a rainforest hunter-gatherer from southwest Uganda, and compared it to the blood of their Bantu-speaking agriculturalist neighbors, the Bakiga.

White blood cells from the two groups were isolated and exposed to Gardiquimod, which mimics a viral infection, and lipopolysaccharide, which simulates a bacterial infection.

The authors observed increased divergence between hunter-gatherers and agriculturalists in their immune responses to viruses, compared to that for bacterial infections. A significant proportion of these differences were shown to be under genetic control and affected by recent positive natural selection.

"These findings suggest that differences in viral exposure may have been key contributors to the divergence in immune responses between the Batwa and the Bakiga populations," said co-author George Perry, Ph.D., an associate professor of anthropology and biology at Penn State.

This study, published July 29, marks the first time the immune systems of and farmers have been compared to help researchers understand how agriculture may have impacted our immune system. The team spent three years establishing connections and discussing mutual research interests with the Batwa and Bakiga prior to collecting any blood samples. The Batwa have lived in settlements along the edges of the Bwindi Impenetrable Forest since 1991, after being displaced from the rainforest. As a result, the researchers limited their Batwa samples to individuals born before 1991 who had actually lived in the forest.

Since collecting the , Barreiro, Perry and other team members have returned to Uganda multiple times to present the results of their research with these communities.

The researchers cautioned that the Batwa and Bakiga populations likely diverged more than 60,000 years ago, long before the origination and spread of agriculture in Africa.

They hope to soon begin similar follow-up studies on additional pairs of hunter-gatherer and farming populations in other areas of the world.


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More information: Genelle F. Harrison et al. Natural selection contributed to immunological differences between hunter-gatherers and agriculturalists, Nature Ecology & Evolution (2019). DOI: 10.1038/s41559-019-0947-6
Journal information: Nature Ecology & Evolution

Citation: Study finds an unexpected link between farming and immune system evolution (2019, August 13) retrieved 23 August 2019 from https://phys.org/news/2019-08-unexpected-link-farming-immune-evolution.html
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Aug 13, 2019
"Instead, the immune systems of hunter-gatherers showed more signs of positive natural selection, in particular among genes involved in the response to viruses"

-Well of course. Humans are a domesticated species, continuously selected over 1000s of gens for their ability to conform to the very unnatural rigors of tribal living. Hunter gatherers are more susceptible to nature than agrarians; their tribes are less complex, less artificial.

Protohuman evolution ended when we became able to hunt the predators that were keeping our numbers in check. Tech-driven overpopulation caused the species to congeal into tribes for protection. Intertribal conflict drove this specific kind of group selection that favored ever larger, more complex and more cohesive tribes. This forced our brains to grow, our physiology to change, and the modern human to emerge.
Cont>

Aug 13, 2019
Much of this change is detrimental, as with many other domesticates. Our brains are delicate and prone to defect and decay. Our immune systems are overactive. Few of us are born pristine, and we accrue damage as we age. And we preserve the weak and unhealthy who would otherwise be lost to natural selection, until they can reproduce.

This explains the wide disparity in cognitive function and many of the medical conditions that plague us today.

Our salvation is that we are becoming able to fix defects in the womb and repair them as they occur. And we can begin undoing the damage that this domestication has caused us by reverting many of these changes genetically and replacing critical systems with entirely artificial parts.

This repair and replace process is unidirectional. There is nothing about the human physiology, no organ or system, that cannot be replaced by a widget that works better because it can be designed specifically for the purpose.

Aug 13, 2019
My fondest hope for you, Otto, is that one day you'll stumble on a college-level textbook of general anthropology (physical, cultural, archaeology) and read it. And take it in.

Your comments would improve a hundred-fold. No, a thousand-fold.

Aug 13, 2019
And you dont know the current state of anthropology and the soft 'sciences'.

"Many (most?) American cultural anthropologists do not consider themselves scientific. Cultural anthropology as it is practiced in many American universities is not a science, so the standard rules of engagement with science do not apply."

-Anthropology is one step removed from the bankrupt discipline of formal philosophy. The job of the typical anthropologist is to collect data and then misinterpret it to suit the current politics. This is why their theories change as often as philos do.

When they can accept:
The human tropical animal
Chronic, tech-driven overpop
Tribalism and intertribal conflict as the creator of the human species
The DOMESTICATED nature of the human species in the context of the tribe

-then they can make some progress. But they can acknowledge NONE of these because they are anathema to contemporary progressive political agendas.
Cont>

Aug 13, 2019
The soft sciences have been devised to manipulate behavior, not explain it.

Not that this isn't important... when left to its precivilized tendencies, the species reverts. Overpopulation and tribalism run rampant. Civilization collapses.

That's the nature of husbandry - to create a species that can suppress it's natural, wild tendencies in favor of the greater good.

The greater good throughout history used to be nothing more than the tribe itself. But intertribal conflict in the context of technology is a powerful form of group selection. Ever-larger and more cohesive tribes would always emerge out of nowhere to assault and destroy emerging agrarian civilizations. See the Sea Peoples, the Germanic tribes and Mongols.

Civilization is maintained today by creating these groups before they can emerge by themselves, and sending them against one another in controlled and constructive ways.

And this is one obvious FACT that few acadeemies suspect and none could ever acknowledge.

Aug 13, 2019
Haven't learned a thing, have you? I feel sorry for you, there in your bubble. Or is it a tunnel?

In any case, what you post here is the wildest BS.

Did you even go to college? I make you for a community college graduate in a technical field of some sort. That's the only way I can understand the vast lacunae in your knowledge.

Aug 13, 2019
And this is one obvious FACT that few acadeemies suspect and none could ever acknowledge
-But a System that all do participate in. Or else they do not participate at all. This too is a form of husbandry, is it not?
Haven't learned a thing, have you?
-And you haven't actually refuted a thing I've said have you? Only invective. That all you got? Too lazy to research?

Aug 14, 2019
And this is one obvious FACT that few acadeemies suspect and none could ever acknowledge
-But a System that all do participate in. Or else they do not participate at all. This too is a form of husbandry, is it not?
Haven't learned a thing, have you?
-And you haven't actually refuted a thing I've said have you? Only invective. That all you got? Too lazy to research?


You're not really worth refuting -- you haven't said a new thing during all the years I've been looking at your comments. Tribes! Yay tribes!

Plus why would I bother refuting drivel? It's still drivel, you still believe it and spout it. What's the point beyond my jerking your chain every now and then. It's fun, and yes I've known all along that it does no good.

You're gonna be the idiot you no matter what.

"when left to its precivilized tendencies, the species reverts." hoo boy. I'd fail this in intro, but you don't even realize how ridiculous (as in 19th century, if that) it is.

Aug 14, 2019
And this is one obvious FACT that few acadeemies suspect and none could ever acknowledge
-But a System that all do participate in. Or else they do not participate at all. This too is a form of husbandry, is it not?
Haven't learned a thing, have you?
-And you haven't actually refuted a thing I've said have you? Only invective. That all you got? Too lazy to research?


You're not really worth refuting -- you haven't said a new thing during all the years I've been looking at your comments. Tribes! Yay tribes!

Plus why would I bother refuting drivel? It's still drivel, you still believe it and spout it. What's the point beyond my jerking your chain every now and then. It's fun, and yes I've known all along that it does no good.

You're gonna be the blah
-Again, no substance whatsoever. You can't refute a single thing I said.

Sad.

Guess it means I know what I'm talking about.

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