Why vestigial structures dont disappear

In other words, there should be vestigial genes. In contrast, the idea that all species were created from scratch predicts that no such genes would exist. This gives us a unique tool to study evolution when we realize that the normal function of a gene is to make a protein—a protein whose sequence of amino acids is determined by the sequence of nucleotide bases that make up the DNA. And once we have the DNA sequence of a given gene, we can usually tell if it is expressed normally—that is, whether it makes a functional protein—or whether it is silenced and makes nothing.

Virtually every species harbors dead genes, many of them still active in its relatives. This implies that those genes were also active in a common ancestor, and were killed off in some descendants but not in others. Out of about thirty thousand genes, for example, we humans carry more than two thousand pseudogenes. Our genome—and that of other species—are truly well populated graveyards of dead genes.

Every month, science journals publish articles describing more such functions. Available online here. Kohtaro Fujihashi, J. McGhee, C. Lue, K. Beagley, T. Taga, T. Hirano, T. Kishimoto, J. Laissue, B. Can you describe your basic ideas or what you understood? I can't really remember what he said. I think the answer is Sometime. Umm, I understand the natural selection concept and whatnot. But I can't gather enough infromation to answer it.

Add a comment. Active Oldest Votes. Evolution is based on four mechanisms : - mutation - natural selection - sexual selection - genetic drift A no longer used structure can disapear if a mutation makes it to. Improve this answer. Manuella Manuella 1 1 gold badge 5 5 silver badges 8 8 bronze badges. It's a safe-house for gut flora following a bout of dysentery, and in places where dysentery is common, it probably saves lives. Sign up or log in Sign up using Google. Sign up using Facebook.

Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. Featured on Meta. They are believed to be leftovers, only vestiges of the past. Evolution is a slow process, with changes in species happening over hundreds or thousands if not millions of years, depending on how significant the change is.

Although many of these types of structures would disappear over many generations, some keep being passed down to offspring because they do no harm—they aren't a disadvantage for the species—or they have changed function over time. Some are present or functioning only during the embryonic stage of fetal development, or maybe they just have no function as we get older.

That said, some structures that were once thought of as vestigial are now thought as useful, such as the whale pelvis or the human appendix. As with many things in science, the case isn't closed.

As more knowledge is discovered, the information we know is revised and refined. The animal kingdom is ripe with vestigial structures in their skeletons and bodies. The human body contains many examples of vestigial structures and responses. The coccyx or the tailbone: Obviously, humans no longer have visible external tails, because the current version of humans do not need tails to live in trees as earlier human ancestors did.

However, humans still have a coccyx or tailbone in their skeletons. In fetuses, any tail is absorbed during development. The coccyx currently serves as an anchor for muscles; that wasn't its original purpose, so that's why it's considered vestigial. Male nipples: All people inherit nipples from both their parents, even males. Natural selection hasn't selected against them, even though they don't have a reproductive use in males.

Goosebumps: The pilomotor reflex, which raises the hair on your arms or neck when you feel alarmed, is vestigial in humans, but it's pretty useful for porcupines who raise their quills at a sign of danger—or birds, who fluff up when it gets cold.

Wisdom teeth: Our jaws have shrunk over time, so we no longer have room for wisdom teeth in our jawbone.