Question

Discuss our body’s physiological adaptation to modern diet. In your answer explain how and why today’s diet is different than what Homo sapiens used to eat 10-12kya. Did we adapt to this diet? If so, how did we adapt (discuss at least 2 different genes in your answer, 300 words, at least 4 academic references in JBC format)?

Answer 1

Our food habit has been changing along the evolution gradient. Before 10000BC, which is almost 12000 years ago modern human were mainly hunter-gatherers. Scientists and researchers have compiled a large amount of evidence which states that along with meat, their food intake comprised of large variety as well as quantity if plant foods (Blumenschine et al., 2006, Dominguez-Rodrigo and Barba, 2006, Marlowe 2006). The age of the hunters came to an end approx. 10,500 years back during the last Ice age. The dietary habit of human kept on changing with the course of evolution, with the learning of the art of cooking, with animal and plant domestication and so on. In order to adapt to this changing dietary system, some genetic adaptation took place. Genetic variation in the genes encoding lactase (LCT) and amylase (AMY1) enzymes are the classic examples of genetic adaptations to the dietary system in the metabolism of Human. The phenomenon that takes place in any animal particularly mammals at the absent of LCT is lactose intolerance. All humans used to lose their ability to digest mother’s milk after getting over weaning that is they stopped producing LCT which breaks down lactose, the main carbohydrate present in milk, into simple sugars. But after humans began cattle domestication approx. 10000 years back, with the availability of ample milk, lactose tolerance evolved independently among cattle herders in Europe, the Middle East, and Africa (Swallow 2003, Ingram et al., 2009). This particular characteristic of lactose intolerance after a certain age is still predominant in all non-human mammals (Buller et al., 1990, Lacey et al., 1994). The enzyme AMY1 is responsible for the hydrolysis of starch in our body as we take them as dietary supplements. This enzyme is expressed both in mouth and pancreases. Now, discrepancies are observed in the human ability to extract sugar from starch, which is dependent on the differential copy number of the AMY1 gene they inherit (Groot et al., 1989, Iafrate et al., 2004). It was observed from tedious studies by Perry et al., 2007, that population that maintained a high starch diet have more copies of the gene than populations that had a relatively low starch diet.

References:

Blumenschine RJ, Prassack KA, Kreger CD, Pante MC. Carnivore tooth-marks, microbial bioerosion, and the invalidation of Dominguez-Rodrigo and Barba’s (2006) test of Oldowan hominin scavenging behavior. J. Hum. Evol. 2007;53:420–426.

Dominguez-Rodrigo M, Barba R. New estimates of tooth mark and percussion mark frequencies at the FLK Zinj site: the carnivore-hominid-carnivore hypothesis falsified. J. Hum. Evol. 2006;50:170–194.

Marlowe FW. Hunter-gatherers and human evolution. Evol. Anthropol. 2006;14:54–67.

Buller HA, Kothe MJ, Goldman DA, Grubman SA, Sasak WV, et al. Coordinate expression of lactase-phlorizin hydrolase mRNA and enzyme levels in rat intestine during development. J. Biol. Chem. 1990;265:6978–6983.

Lacey SW, Naim HY, Magness RR, Gething MJ, Sambrook JF. Expression of lactase-phlorizin hydrolase in sheep is regulated at the RNA level. Biochem. J. 1994;302(Pt. 3):929–935.

Ingram CJ, Mulcare CA, Itan Y, Thomas MG, Swallow DM. Lactose digestion and the evolutionary genetics of lactase persistence. Hum. Genet. 2009;124:579–591.

Swallow DM. Genetics of lactase persistence and lactose intolerance. Annu. Rev. Genet. 2003;37:197–219.

Groot PC, Bleeker MJ, Pronk JC, Arwert F, Mager WH, et al. The human alpha-amylase multigene family consists of haplotypes with variable numbers of genes. Genomics. 1989;5:29–42.

Iafrate AJ, Feuk L, Rivera MN, Listewnik ML, Donahoe PK, et al. Detection of large-scale variation in the human genome. Nat. Genet. 2004;36:949–951.

Perry GH, Dominy NJ, Claw KG, Lee AS, Fiegler H, et al. Diet and the evolution of human amylase gene copy number variation. Nat. Genet. 2007;39:1256–1260.