Ask a Question
or
Create a Poll
  1. Home /
  2. Questions /
  3. Science
  4. / Biology
  5. / Human Evolution
  6. / General Human Evolution

by R Spandit on April 3rd, 2006

R Spandit

Question

Help answer this question below.

Is it likely that the basic human cell evolved from just one animal, or is it a combination of animals that once lived together in symbiosis?

Share:
Other

Answers. Showing one answer.

  • by lynnenorth on April 7th, 2006

    lynnenorth

    All animals' cells contain mitochondria, which we believe were once free-living prokaryotes. Now they are fully integrated into our cells, to the point that we could not live or function without each other. The biologist Lynn Margulis managed to bring this "outsider theory" into orthodoxy by the sheer weight of her evidence for it, so that model is currently well accepted.

    The eukaryotic cell nucleus itself may have been the result of the fusion of two different prokaryotic cells, but that model has only recently been hypothesized and is still largely speculative.

    Aside from that, mammalian cells in general and primate cells in particular contain some DNA which we think originated in viruses and was permanently written into our genome by those viruses. As much as 40% of the human genome is composed of what we call "retrotransposons" -- snippets of DNA which create copies of themselves in more areas of the genome, by creating a mobile RNA element which finds another place along the strand of DNA to plug itself in, then acts as a template for more permanent DNA. Some of these retrotransposons bear a distinct resemblance to the genomes of certain viruses which are still free-living. For example, see http://www.hhmi.org/news/cullen.html for information about the HIV-like snippet of code which has been part of our own genome for many millions of years, and the HERV-K (for human endogenous retrovirus K) family of viruses which have taken up permanent residence.

    This is closer to parasitism than to symbiosis, however. There are indications that the insertion of virus DNA can add to the variability of our genome and affect the function and regulation of our genes (sometimes in a bad way, but sometimes in a way which, just by accident, makes our genes more "effective" at whatever they code for). But for the most part, they don't seem to do much except use our cells' machineries to reproduce themselves.

    Aside from these things, I would have to say no, we don't tend to recombine cells between animals outside of normal reproduction with sperm and egg, no matter how closely we are associated. For example, we have large and thriving ecosystems of bacteria living on our skin and in our gut, and we couldn't function without the gut flora and fauna, but not only do these prokaryotes remain separate organisms, our genomes have remained separate as well as far as we can tell.

    Comments

    • Interesting, and clearly a huge and diverse field of study

      R Spandit

      by R Spandit on May 2nd, 2006

    • Well done.

      Moongrim

      by Moongrim on December 31st, 2009

    • Like
    • Report

    2 comments | Post one | Permalink

Want to attach an image to your answer? Click here.

Did this answer your question? If not, then ask a new question or create a poll.

More Questions. Additional questions in this category.

You're reading Is it likely that the basic human cell evolved from just one animal, or is it a combination of animals that once lived together in symbiosis?

Follow us on Facebook!

Related Ads

Related Questions

Professionally Researched

Answerbag

a Demand Media company