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Gary Larson

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It’s not just skin deep: the unintended effects of agriculture on our genome

As mentioned previously, Culture Gene Coevolution theory is the idea that through our culture, we are actively creating selective pressures on ourselves, selecting for genes in a much faster rate than evolutionary pressures alone. We illustrated this through the presence of high rates of lactose persistence in geographical regions where humans have been dairying for longest time. I’d like to return to gene-culture evolution in a way that analyzes what might change about our bodies in light of some the modern agriculture practices we see today.

I’d like to introduce you to a different example of gene culture evolution, the rise of Sickle Cell disease in response to increased agriculture. When humans first began clearing land, lack of trees resulted in an increase in standing water, especially in places that receive heavy rainfalls, which therefore attracted mosquitos many of which carried a virus called malaria. Geographical concentrations of sickle cell are shown to be in Mediterranean areas as well as large portions of Africa. With high mortality rate of malaria, there was a selective pressure for the variant of hemoglobin that allows blood cells to be resistant to contracting malaria, HbS (“normal” variant is HbA), because of their sickle shape. Those with the HbS variant had higher resistance, therefore less mortality, and therefore higher instance of survival and more reproduction. Individuals who are heterozygous for sickle cell (one parent passes on HbA, one parent HbS), have highest resistance as well as relatively normal blood function, however, those who are homozygous (HbS from dad, HbS from mom) have sickle cell disease that interferes with oxygen transport in the blood. This human response from an unintended agriculture consequence makes me question if my example of the pig farm in my previous post, might have unintended consequences in gene expression in resistance to e. coli, much like what we saw with sickle cell.

According to a 2016 Duke University study, some people may have immunity genes that keep them from becoming ill when exposed to e. coli, a potentially dangerous bacteria that has claimed lives and often results in massive recalls of foods upon discovery.

My question is how the population who lives in very close proximity to these pig farms might respond to the constant exposure to the untreated animal waste that holds plenty of bacteria, including e. coli?

As discussed in the video in the previous post, there have been many reported health issues associated with the spraying of the waste, with the most research being conducted on the prevalence of asthma in these areas. However, how do we consider this exposure to bacteria with a coinciding natural bacteria resistance?

My assumption, based on the evidence of sickle cell, is that people who are sensitive to e. coli may have higher rates of death when exposed, as has happened recently in the recall of e. coli infected romaine lettuce in the United States. Therefore, people with natural resistance would be left to have higher rates of survival, and in turn higher rates of reproduction and passing on the natural e. coli resistance. So, in these areas closest to pig farms with highest exposure, hypothetically, we would see increased percentages of e. coli resistance, much like how we saw geographical dispersion of lactose persistance. This theory could be applied to the many toxic bacteria that are present in the waste. It is well known that environmental effects play a large role in asthma prevalence, but it is also may have genetic ties, allowing for further speculation if selection genes that induce allergic asthma would also be selected against.

I hope that we can begin considering our agricultural choices through a Niche Construction and Culture Gene Coevolution theoretical frame work, for us to appreciate what might be the lasting consequences not only on the environment, but our bodies, in the millennia to come. We as humans are the ultimate niche constructors with power to manufacture and change our environments unlike any other species, and while spectacular, our capabilities may have grown to a point where our own actions that we glorify might just turn around to bite us back.

 https://www.healthcentral.com/article/how-genetics-affect-asthma-doctor-qa

https://corporate.dukehealth.org/news-listing/immunity-genes-could-protect-some-e-coli-while-others-fall-ill

https://www.thecut.com/2018/04/what-to-know-about-the-romaine-lettuce-recall-and-e-coli.html

Michael J. O’Brien and Kevin N. Laland .Genes, Culture, and Agriculture: An Example of Human Niche Construction .Current Anthropology. 2012 .               

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Agriculture as the Human Niche: Long Duree Impacts Of Agriculture on Ecosystems

In my last blog post, I introduced the theory of Niche Construction, concluding that agriculture is the very powerful human niche, and it’s influence changes both the world we live in and our bodies. This post’s purpose is to analyze agriculture’s lasting impact on landscapes and compare past agriculture practices to today’s and contemplate what we might leave behind for humans to see in a thousand years from now.

Well, First Things First. In order to even begin the systematic agriculture, we need a plot of land with fertile soil to plant our seeds. We need land that is accessible, differentiated from forests to be able to closely monitor and domesticate our chosen seedlings. How do we create these cleared lands? At least in the beginning, primarily through fire. Burning lands in closely managed ways can have many benefits like increased plant and animal biodiversity in the years to come when the forest eventually grows back. However, agricultural land clearing does not have the intention of letting these natural ecosystems recover, their clearance is maintained over long periods of time. This changes the composition and dispersal of plant species, including increased expansion of species that were cultivated by humans and changes in DNA structure due to selection forces by humans.

When we clear land, we are also disrupting the ecosystems within which animals live, and consequently having an impact on their evolutionary trajectory. By deforestation, we created an anthropogenic natural selection force, with examples including increase in selection for faster game, and decrease in body size due in tortoises, otters and limpets due to overhunting of the larger within species. Another glaring point is that due to overexploitation, many species, particularly megafauna, have gone extinct in the wake of anthropogenic forces.

But how has intensified agriculture affected the landscape itself?

In a case study of the recovery of New York forests that were once cleared for agriculture but had been allowed to regenerate, the lasting impact was in a distinct difference in organic matter composition in the soil and biodiversity of the trees that had grown back

“The principal legacies of agriculture that remain in these forests are the reduced levels of soil organic matter, carbon, and phosphorus; the spatial homogenization of soil properties; and the altered species composition of the vegetation.” (Flinn and Marks 2007)

 In Bovin et al it is mentioned that “expansion of land area used for livestock and rice paddy agriculture was sufficient to increase atmospheric methane emissions between 4,000 and 1,000 y B.P. whereas deforestation and tillage are suggested to have contributed to increasing CO2 over the past 8,000 y .”(Bovin et al, 2015)

Obviously, This rice paddy is an incredibly large structure that has left extensive scars on the ground along with chemical changes. In light of this, I encourage everyone to contemplate the long durée consequences of large scale animal agriculture is having on our environment.

Currently, 60% of animals on earth are farm animals. What are the implications of this in terms of future recovery and animal biodiversity? How is animal agriculture producing selective pressure on the animals we farm, and also the animals we don’t?

Currently, 30% of Earth’s land is used for animal agriculture, with seven football fields of land bulldozed for space for animal agriculture every minute. When we consider that we are creating strong selective pressure for our major crops (wheat and soy for example) what might this mean for future plant diversity with this new selective anthropogenic pressure?

In terms of animal recovery, we can say two things. Through deforestation, we are forcing many animals to extinction, and when we consider niche construction and these animals actively engaging with and modifying their environments, the absence of these animals will have effects on the landscapes they contribute to and also have effects on surviving lineages in absence of the selective pressure. Animals we do domesticate, have undergone extensive DNA changes, for traits such as less aggression and for a substantial increase in size that often leaves them incapacitated. I wonder how these animals could survive in a world without humans, when they have been bred to dependent upon our care?

https://youtu.be/ayGJ1YSfDXs 

Although this video is concerned with public health, which is an extremely important consequence of this irresponsible environmental action, I encourage readers to consider how this human agriculture induced pollution will show in the archaeological record, and the lasting effects it will have on the environment.

How might this large waste pond that holds the waste of thousands of livestock animals affect soil fertility and plant species diversity if this area is ever left to recover? 

How might we see these impacts in terms of their presence and impact on the archaeological record? 

I suspect that at least this particular example, there would be extensive dark earthing, which will effect stratigraphy and the morphology of soil, which as explained above, will have impacts on the plant and animal recovery and biodiversity in these areas.

 Dambrine, E. , Dupouey, J. , Laüt, L. , Humbert, L. , Thinon, M. , Beaufils, T. and Richard, H. (2007), “Present Forest Biodiversity Patters in France related to former roman agriculture. Ecology, 88: 1430-1439. doi:10.1890/05-1314

Flinn, K. M. and Marks, P. L. (2007),” Agricultural legacies in forest environments: tree communities, soil properties and light availability”. Ecological Applications, 17: 452-463. doi:10.1890/05-1963

Nicole L. Boivin, Melinda A. Zeder, Dorian Q. Fuller, Alison Crowther, Greger Larson, Jon M. Erlandson, Tim Denham, Michael D. Petraglia. “Human shaping of global species distributions”. Proceedings of the National Academy of Sciences Jun 2016, 113 (23) 6388-6396; DOI: 10.1073/pnas.1525200113

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I’m researching & drawing my way through the history of the first prairie restoration, the Curtis Prairie at the University of Wisconsin Arboretum in Madison, WI. More to come! ✨💛🌾💛✨

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The beginning

Agriculture

It’s what has long been appreciated as the unprecedented turning point for human evolutionary trajectory.

When we learn about human evolution in linear succession we hear:

Monkey ➝ Walk Upright ➝ Fire ➝ Agriculture ➝ *ta-da* HOMO SAPIEN!

This rhetoric is ingrained into those of us who were taught evolution in middle and high school, the common knowledge that scholars have proven and accepted. There’s no doubting that the rise of agriculture allowed our ancestors new opportunities not available to other hominins. A power play that put us (at least we perceive it that way) in a position of dominance in the battle for survival. We could now not have to spend the entirety of our existence searching for our next meal to survive, at the mercy of what the land wanted to provide. We could instead spend time creating what would turn into the world as we know it today, through reading, writing, art, craft specialization, building villages that would turn into cities that would someday turn into kingdoms. We began institutionalizing our morals, law, customs, world views - creating identifiable culture.

We finally had a say in our future. We can thank agriculture for today’s society.

The opportunities for mental growth and the growth of society that agriculture gave us are well appreciated. But what are the environmental repercussions of agriculture on the landscape and therefore us. How has agriculture and food sustenance changed our bodies? Some researchers believe that the human capacity for culture is evolutionary process in its own right. This evolutionary pressure effects all animals in the ecosystem being modified, wild animals, the animals we domesticate, plants and that’s right, even us.

This theory is called Niche Construction theory and is defined as “a fledgling branch of evolutionary biology that places emphasis on the capacity of organisms to modify natural selection in their environment and thereby act as co-directors of their own, and other species', evolution... Organisms also produce, modify, and destroy habitat and resources for other living creatures, in the process driving co-evolutionary dynamics.” (Laland, O’Brien 2010). For example, cyanobacteria, by producing oxygen, inadvertently helped create the oxygen rich environment that allowed for well, just about all of us on Earth, to survive. 

thank you, cyanobacteria!!

This can also apply to humans. Agriculture is an intense land modification, the way we harvest food and treat the soil has lasting effects on the environment. Which foods we choose to domesticate and which ones we don’t, which animals we choose to domesticate and which ones we don’t, where create settlements and where we don’t, all play a role in not only constructing environments, but changing our behavior and potentially our genes. The theory concerning itself with how culture can change us down to our DNA, is  Gene-Culture coevolution. The idea that our cultural behaviors can overtime, affect our DNA. One striking and common example is the loss of lactose intolerance in adults, when humans typically lost their ability to digest lactose as toddlers when we stopped breastfeeding. Researchers, Simoons (1970) and McCracken (1971), noticed that there was geographical dispersion of lactose tolerance/intolerance. In northern Europe, where populations have been dairying for hundreds of years, people had the highest percentage of lactose tolerance. Their agricultural choices had created a preference for selection of the gene that allowed adults to drink milk.

With this in mind, how might current agricultural practices not only alter our ecosystems, but also alter our bodies in response?

Laland, Kevin N., and Michael J. O’Brien. “Niche Construction Theory and Archaeology.” Journal of Archaeological Method and Theory, vol. 17, no. 4, 2010, pp. 303–322., doi:10.1007/s10816-010-9096-6.

O’Brien, Michael J., and Kevin N. Laland. “Genes, Culture, and Agriculture.” Current Anthropology, vol. 53, no. 4, 2012, pp. 434–470., doi:10.1086/666585.