None of the children are adopted just one of the them got both of there parents blood types
The answer is cellular aging theory. This theory focuses on the ways then that the molecules as well as the cells are being affected by aging and the passage of time. Aside from this theory there are 2 more theories of aging namely the genetic theory and the wear and tear.
It's harder to find one of the many genes involved in a polygenic trait vs the only gene involved in a discrete trait.
That the birds are named after the color of there feathers