Monday, July 4, 2011

Endogenous Retroviruses

If I were asked to present the single line of evidence that best supports common descent, endogenous retroviruses (ERVs) would probably be my choice. They attest not only to evolution in general, but to human evolution specifically and even to the age of the earth—and they present a potential point of falsifiability.

Retroviruses reproduce by inserting their genetic code into a cell's DNA. In rare cases, they happen to do this to one of the host organism's germ line cells (which become sperm or egg cells). When that organism reproduces, the retrovirus' genetic code is passed down to future generations. The retrovirus is now an ERV, which then lies dormant in the genome, slowly accumulating mutations just as the rest of the DNA sequence does. ERVs are essentially genetic fossils, remnants buried not in the ground, but deep within every cell of the body.

We know ERVs are actual remnants of viruses—and not just because they look exactly like viruses, although that should be evidence enough. In 2006, a team of French scientists actually revived an ERV from the human genome, which they dubbed "Phoenix." When introduced to a cluster of human cells, Phoenix was able to infect them—which would of course be impossible if Phoenix wasn't a real virus that actually infected one of our distant ancestors.

Even if ERVs didn't demonstrate our common ancestry with other animals (I'll get to that in a minute), they'd still be completely incompatible with a 6,000 year old earth. They make up almost 8 percent of the human genome in the form of 98,000 fragments from 30,000 retroviruses—and everyone's ERVs are more or less the same, give or take a few mutations. For that many viruses to insert themselves into just the right sperm or egg cells and spread evenly throughout the entire population would take several orders of magnitude longer than the young-earth paradigm allows.

So why are ERVs important evidence for evolution? Simple: they're arranged in patterns called nested hierarchies, and there's no reason to expect to such patterns unless common descent is true. If an ERV shows up in one species, which later splits in two, it will show up in both "daughter" species. For example, in the graph below, some specific ERVs are found in gibbons, orangutans, gorillas, chimps, and humans, because the virus infected the common ancestor of all five. Some ERVs are found in just the latter four, some in just the latter three, and so on. What's more, we find them in the exact same location in the genome of each species, meaning that the virus didn't happen to somehow infect them independently.

From Lebedev et al 2000. Time goes left to right.
Arrows represent ERV insertion at specific points in the genome,
which carry over to all subsequent species in that lineage.
At no point should we ever expect the same ERV in the same location in, say, humans and gibbons but not chimps—and we don't. The same goes for any two species that don't share a direct common ancestor, and the pattern holds each and every time. Let no one ever tell you that evolution is unfalsifiable; if the above examples turned to be true for some ERV, it would be completely unexplainable by common descent. However, the nested hierarchies we do find beautifully match the ones formed by other types of evidence.

So there we have it: ERVs point powerfully to an old earth, human evolution, and common descent in general. Naturally, creationists have tried to undermine this evidence, and as usual they fail miserably. I've already answered one objection (that they were never viruses at all), but these two blog posts by a graduate student specializing in ERVs offer a better response than I ever could. It saddens me that so many people—40% in America—believe in strict creationism, when most of them have never so much as glanced at the extraordinary evidence available.

1 comment:

  1. sorry for my english. i have some interesting points about the creation-evolution topic.

    the evolutionist always says that a watch need a designer because it cant self rplicat but organisem do self replicat and has dna so they can evolve. but according to this claim: if we will find a self replicat watch(with dna) we need to say that is made by itself .but we know that even a watch that self replicat itself is evidence for design.

    scientist even find a motor in bacteria called bacterial flagellum:

    and we know that a motor is evidence for design. even if its very small and made of organic material.

    the evolutionist claim that small steps for milions years become a big steps. but according to this a lots of small steps in self replicat car (with dna) will evolve into a airplan.

    but there is no step wise from car to airplan

    evolutionist claim that common similarity is evidence for common descent. but according to this 2 similar (self replicat) car are evolve from each other and not made by designer. and we even share 50% with banana!

    about order in fossils record- we can make order in cars. for exmaple: a car--> a jeep--> a truck.but its not proove that they evolve from each ohter

    check this site:

    what do you think about it? have a nice day