Darwin’s Surprise

I think that the article is titled “Darwin’s Surprise” because Darwin “might be surprised to learn that humans are descended from viruses as well as from apes (Specter, 2007)” as Robin Weiss put it. He had moved to the jungles of Malaysia and lived among a group of Orang Asli tribesmen who were skilled in trapping chickens. One of the species of chickens there were red jungle fowl, who were an ancestor species of chickens. Weiss was able to identify the versions of the same viruses in the red jungle fowl and similar results were found on other animals. Darwin had believed that humans and apes shared a common ancestor in “The Descent of Man” but I think he would have never guessed that the common ancestor would be viruses.

The article talks about how endogenous retroviruses are parasites and that they are found in large quantities in tumors which obviously shows that cells are better off without them, except for one exception. Then the article continues to go on about placentas and this is where I thought was the most surprising part of the article. According to Spector, the earliest mammals laid eggs but then instead of growing inside the shell, embryos became parasites and implanted themselves in the lining of the womb as balls of cells. Those cells became the placenta which allows embryos to receive nourishment from the mother while preventing harmful bacteria from going in. Biologists in the 1970s found retroviruses on a layer of tissue that separates the mother from the fetus in baboon placentas, and the animals were healthy. This was also found on other mammals such as mice, humans, and cats.  Throughout the beginning of the article I was under the impression that *all* retroviruses were harmful, since the one that everyone knows of is H.I.V and has claimed many lives, but retroviruses are also beneficial as seen on placentas. The article even mentions that the same mechanisms are seen in both placental cell fusion and the attachment of retroviruses onto the cells they infect.

Endogenous retroviruses infect the DNA of a species and then become a part of that species. However, they do become defeated and only fragments are left which reside in all of us, serving no purpose. However, Thierry Heidmann and his team took one of the viruses out of extinction, figured out how the broken parts were originally aligned, and then pieced them together (Spector, 2007). They then placed in human cells and saw that the virus became a part of the DNA of those cells. They mixed the virus with cells of other animals and in turn those cells also became infected. Combined with the possibility of viruses being the common ancestor, the role viruses have played in evolution has been ongoing since the very beginning of life. By bringing extinct viruses back to life, those viruses can provide a history of the “origins and evolution of humanity”. Heidmann also argues that viruses shaped the way we are today due the virus’s role in the creation and development of a placenta. This lead to live birth which is a definite stepping stone in human evolution. This has changed my view and understanding of viruses since viruses are known to be nonliving, since the one thing they do best is evolving yet they can provide information on the evolution of mammals and humans.

I do think that science should revive dead viruses to gain information on modern day viruses such as H.I.V and how humans evolved. If our body is littered with so many fragments of broken and disabled retroviruses that fused and became a part of our DNA, this could one day happen to H.I.V at a much faster rate than thousands of generations. Reviving dead viruses could also help with looking at the beneficial effects of retroviruses such as the placenta and could also help with modern day medicine. It would also provide so much evidence and additional details that had not appeared on human evolution. Humans share most of the viral fragments with apes such as chimpanzees and monkeys, but what chimpanzees have and what humans lack is a copy of a virus called Pan troglodytes endogenous retrovirus (pterv) which allows chimps to be infected by the AIDS virus but never become sick. It turns out that pterv infected gorrilas and chimps 4 million years ago, but there is no sign of it infecting humans. With this knowledge it shines more light on our knowledge of AIDS and help combat it through reviving it and allowing our bodies to accept it. HIV/AIDS would just be the beginning if science revived dead viruses.

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One Response to Darwin’s Surprise

  1. TonD says:

    I totally agree with your awe at the evolution of the placenta in mammals. To know that viruses actually helped mammals into dominance with the introduction of the placenta gives them a whole new light. This brings up a question: why are there still mammals that lay eggs? Well actually, I am only talking the platypus. From my knowledge, they are the only mammals that do not have a placenta. I can attempt to come up with an explanation. Because platypuses live almost exclusively in a water environment, they are separated from most of the other mammals. When the virus responsible for the placenta came to infect mammals, the platypus was spared due to its isolation. This is probably the point of divergence. Again, this is probably totally wrong. The idea just came to my head and I am not really sure why laying eggs and prove to be advantageous to a mammal.

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