Humans and dolphins share the same homologous
trait in the structure of their bones in their outer limbs. These two
structures perform very different tasks and are laid out in a different way but
the key structure is the same. They share the same bones such as a humerus,
ulna, and phalanges. While humans use their hands, and the bones in them, to
grab items and write; the dolphin uses the bones in their pectoral fins to turn
and stop in the ocean. They also use their “flippers” to control their body
heat in changing water temperatures. The different environments of the dolphin
and the human are what contribute to the vastly different uses of these similar
bones. Dolphins have no need to write or type papers so they evolved to use their
bones in a different way. Humans use their legs to propel them forward or turn
so we evolved to use our arm and hand bones to do other meaningful tasks. There
have been many studies done about the commonality between dolphins and humans,
but I unfortunately could not find a definitive common ancestor. Many think the
dolphin first lived on land while others think that humans came from the sea.
If I were to make an educated guess, I think we could share an aquatic
ancestor.
Penguins and fish fins are an example of analogous
traits. Both of these animals have evolved to use fins that help them pilot
through the waters. Penguins uses there flightless wings to dart through the
water with extreme dexterity and precision. The common fish uses its fins in
the same way. They use the fins on the side of their body to help them turn and
move through the water. The locations of these structures are also very
similar. Both animals have these fins on the side of their body.
A common ancestor could have possessed this
trait or one very similar to it. That could explain the similarities between
the dolphin fin and human arm as well. All of these structures share some
similarities. However we know that the penguin and fish are not homologous.
They most likely share this trait due to similar needs and environmental factors
that cause both species to evolve and have fins.
Good description on your homologous trait. You don't have to get too complicated to understand the issue of ancestry, and no, our common ancestor was NOT aquatic (this is called the "aquatic ape theory" and has been thoroughly debunked). Humans and apes are both mammals. All mammals share a general, inherited limb structure, which you describe in your post. That is all you need to demonstrate common ancestry.
ReplyDeleteOkay on your description of you analogous structure.
"A common ancestor could have possessed this trait or one very similar to it. That could explain the similarities between the dolphin fin and human arm as well."
But then, these traits wouldn't be analogs, they would be shared traits inherited from a common ancestor. In order to be analogs, traits have to share similarities do to common function, NOT due to ancestry. If both penguins and fish inherited their fins from a common ancestor, they would not be analogs. The common ancestor of these two organism would be a very early fish, so the ancestor did possess the basic fin structure. But we also know that penguin "fins" are actually derived bird wings. In other words, penguin "fins" arose independently from that common fish ancestor and therefore these are analogous traits.
Make sure you understand the significance of ancestry in determining the homologous or analogous status of these traits.
The understanding of how a human and a dolphin have similar limbs and bone structures is quite interesting. Who knew that we have the same structure as a animal that lives in the sea.
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