Scientists are able to control hierarchy in rhesus macaques. They do this by introducing monkeys into groups one at a time, and at least initially the monkeys that are introduced first have higher status.
Now here's the amazing thing.
Scientists then found that the genes in higher ranked monkeys are expressed differently than the genes of lower ranked monkeys. This is the result of epigenetic changes in which genes are methylated differently in monkeys with different status.
In fact, scientists are able to determine the social status of a monkey with 80% accuracy purely from blood samples.
Moreover as monkeys change their social ranks, the expression of their genes also change. Finally, it turns out that many of the genes that are affected by social status have to do with the immune system, and that monkeys with lower social status have weaker immune systems and tend to die of disease earlier.
There is growing evidence that the same is true of humans. It's not the workaholic CEO who dies early, but the guy who doesn't make it.
- J. Tung, L.B. Barreiro, Z.P. Johnson, K.D. Hansen, V. Michopoulos, D. Toufexis, K. Michelini, M.E. Wilson & Y. Gilad "Social environment is associated with gene regulatory variation in rhesus macaque immune system"