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Name: Tyler
Status: Other
Grade:  Other
Location: Outside U.S.
Country: Canada
Date: Fall 2010


Question:
I'm simply a curious party that heard a rediculous claim on some U.F.O. documentary and the subject of human/alien hybrids came up with people talking about a skull they found which they claim to be a hybrid skull. They said it was over 900 years old, and that the Mitochondrial DNA in it was strange in that the DNA from the human mother was there, but not the supposedly alien father. My question is just to settle my stupid-theory-struck brain. How long does it take for any recoverable human DNA to decay?



Replies:
Tyler

Human, animal, and plant DNA all same stuff, just in different physical arrangements. So that distinction is not relevant.

I did a Google search on "Oldest DNA Found" and found this credible article that reports the discovery of some bacteria DNA that is 419 million years old has been found.

http://news.discovery.com/earth/oldest-dna-bacteria-discovered.html

I also found this article from Popular Science magazine that reports the discovery of the oldest HUMAN DNA "found in the New World" comes from copralites found in a cave in Oregon. Copralites are dried excrement. This sample tested at 14,300 years old.

http://www.popsci.com/scitech/article/2008-04/oldest-human-dna-found-americas

Scores of other sites of interest that resulted from this Google (http://www.google.com) search also showed up and are interesting.

So, to answer part of your question, YES, 900 year old DNA is a possibility.

You are right to ask about the credibility of sources of information especially in this day of mass media. There are a lot of claims by people and legitimate organizations (such as pharmaceutical companies) with dubious motivations and even fraudulent credentials in the public media. I find especially amusing the Discovery Channel and History Channel's interviews with "UFOlogists" a new but yet unrecognized scientific field. So when you are reading articles like this, consider all of the proposed "facts" and look for inconsistencies, contradictions or really ridiculous claims such as a 25 year old providing an eye witness report of something that purportedly happened 100 years ago. Another earmark of a bogus report is the citation of irrelevant facts in the story to fill in the space required to make the article long enough for publication. Most of the time these techniques are not hard to do.

Now for the 2nd part of your question: I grew up in Roswell, New Mexico between 1947 and 1964. I heard the stories about the local UFOs and while in the 7th grade, while 9 years old in 1956, I went to the local library and found some books on UFOs and concluded that the stories were bogus. I have been listening to these stories for 55 years now and I have decided to reject all UFO stories until at least one single piece of physical evidence was presented before I would begin to consider the possibility of alien visits to Earth. So far I have seen nothing. Something as simple as a hand calculator prior to 1970 when the rest of us were using slide rules.

It is always pertinent to ask, who conducted the study and what is the source of their funding, especially in today's mass media world.

Sincere regards,
Mike Stewart

PS Can you pick out the inconsistency in my answer? Please note my first citation is from DISCOVER.com while in the next paragraph I question DISCOVER channel's reliance on testimony from "UFOLOGISTS." But I feel confident that the article is valid because it presents a lot of consistent facts.


Tyler,

I think the more amusing part of the tale you tell is about mitochondrial DNA. Mitochondrial DNA is passed only from the mother (not the father). So the program's "shocking" claim is actually very well understood biology.

Although I did not see the program you describe, many similar programs use a mix of part-truths and willful misrepresentation (like this program has, describing the paternal mitochondrial DNA as "inexplicably missing"). I would recommend a large measure of caution and skepticism in how you approach this.

However, to answer your direct question, there are biological techniques that can tell you a lot from even highly decayed DNA. DNA does decay relatively quickly, but even a sample that is 900 years as you cite could yield important information. It all depends on what you're analyzing, how you're analyzing it, and the particular degree of decay from your sample.

Hope this helps,
Burr


Mitochondrial DNA is always inherited maternally.

Mitochondria are organelles inside our cells. They contain mitochondrial DNA, in addition to the chromosomal DNA.

A sperm cell is small – a nucleus containing 23 chromosomes (in humans), and very little cytoplasm. It swims as fast as it can to win the race and fertilize the egg. It does not carry mitochondria because it travels light and they would slow it down.

An ovum (egg) is larger; it contains 23 chromosomes in the nucleus of the cell, surrounded by lots of cytoplasm, including mitochondria with mitochondrial DNA.

(Humans: 46 chromosomes, 23 inherited from Mom and 23 inherited from Dad; other species have different numbers of chromosomes per cell.)

Occasionally parents of different species might produce a hybrid, e.g., a male donkey and female horse produce a mule, whose nuclear DNA is half donkey and half horse, and whose mitochondrial DNA is all horse. Different species, but still they are earthlings, not aliens.

The fossil skull most likely had an earthling father of the same species as its mother. Its chromosomal DNA would have been inherited equally from both parents. Its mitochondrial DNA would have come only from its mother.

Sarina Kopinsky, MS, CGC (genetic counselor)
DENVER GENETIC LABORATORIES



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