Question

is it true that the little opposum embryo starts off with only 1 ear bone, then as it develops, 2 bones from the jaw move to the middle ear to become other other 2 ear bones we see in all mammals, beautifully illustrating and representing 300 million years of evolution?

Answer 1

Yes, the development of an opossum embryo and the formation of its three middle ear bones from the jaw illustrate a process that encapsulates evolutionary history. The single ear bone in early development becomes three in mammals, a change which traces back to their ancestral lineage. This is an example of how embryology provides evidence of common evolutionary origins.

Step-by-step explanation:

It is indeed true that embryonic development in mammals reflects evolutionary history, which is beautifully illustrated in the development of the middle ear bones. In early embryonic stages, all mammals, including opossums, initially form a single ear bone known as the stapes. As development progresses, two additional ear bones, the malleus and incus, arise from bones that are originally part of the jaw. This transformation is a vestige of evolutionary change, where these bones in ancestral forms functioned in the jaw and over time migrated to the ear in mammals. Specifically, the malleus evolves from the articular bone, and the incus from the quadrate bone.

Embryological evidence supports the fact that vertebrae embryos, including humans and other animals, exhibit gill slits and tails at some stage of their early development. This commonality echoes our shared evolutionary ancestry with other vertebrates. Embryological similarities such as these are some of the oldest evidence of evolution we possess, complimenting fossil records and genetic data.