Blah, blah, blah

Researchers from the University of Manchester found that parents tend to favor the eldest offspring–in beetles at least. “Parents show bias in sibling rivalry, Study says.”

Nicrophorus vespilloides.

Because beetles form families with two parents and many offspring, the lead researcher Dr. Per Smiseth thinks that this research may offer insight into human parental relationships: “The burying beetle Nicrophorus vespilloides has a similar family structure to that of a human family unit in that there are two parents, a number of offspring and interactions between parents and their young.”

They do acknowledge that human relationships and family structures are more complicated, but the basis of their association of human and beetle is on a social construct of what the human family is. Not everyone is raised by two parents (single parent households, polygamy, adoption, sperm donors, egg donors, etc.) and not everyone has siblings, so I highly doubt you can summarily conclude that beetles and humans have similar family structures.

The researchers found that when parents were removed after the eggs hatched, all of the young beetles ate equivalent amounts of food and grew to an equivalent size. However, when parents were left with their offspring, the elder offspring ate more and grew to a larger size because the parents fed the eldest more.

The study offers two theories to explain this preferential feeding: (1) the parents assign some greater value to the elder offspring; and (2) the elder offspring are stronger and can dominate younger offspring and attract the attention of their parents.

I think it is shaky reasoning to extrapolate from beetles to humans to suggest that parental bias is biological. If parents do favor one child (sex/age/size/etc), how could you isolate it from their lived experiences and claim it biological? Plus, why would humans be more similar to beetles than any number of animals that do not have differential treatment of their young or have the opposite preference?

I did find it slightly funny and timely, though, because my little sister recently told me that she thought my mother favored our oldest brother (the eldest), who is overweight (whereas my little sister and I are not).