Developmental homeostasis
Developmental homeostasis is a process in which animals develop more or less normally, despite defective genes and deficient environments.
[2][3] Due to the fact that survival of the species is based on the ability to interact with their own kind in a normal manner, these experiments—which usually interfere with that—walk a fine line for animal rights and what is acceptable.
One way physical developmental homeostasis was tested was in the facial symmetry experiment where people were asked to rate which of the faces they saw as better looking.
In species that value developmental homeostasis, both physically and mentally, the ability of one to adapt to social norms seems to increase the likelihood of having a reproductive advantage at being able to attract mates and leave offspring.
In a short period of time the monkeys took on side effects of weight loss and abnormal physical development.
Once the monkeys reached an age where they could eat solid foods, they were separated from their cloth mothers for three days.
The surrogate-raised monkeys exhibited depression and aggressive behavior as they would clutch to themselves, rock constantly back and forth, and avoid interaction with others.
[1] In 1960, Harry Harlow began studying partial and total isolation of infant monkeys by raising them in cages.
The results showed that when the monkeys were placed in partial isolation they displayed various abnormal behaviors such as blank staring, circling in their cages numerous times, and self-mutilation.
This could be due to the ability to find prospective mates in responding positively to either body or facial symmetry.
Men and women find traits such as averageness, symmetry, and masculinity (in males) or femininity (in females) in faces attractive.
Disruptions to development caused by mutations or by an inability to secure critical material resources early in life could generate asymmetries in appearance.
If body asymmetry reflects sub-optimal development of the brain or other important organs, a preference for symmetrical traits could enable the selective individual to acquire a partner with "good genes" to transfer to their offspring.
For example, barn swallow females have been reported to prefer males whose long outer feathers are the same length on each side.
[12] One species that chooses their mates based on body symmetry is the brush-legged wolf spider.
