Paul Lynde was a Herculeeze compared to the rest of us, don't cha know...
Posted on 10/05/2002 11:42:03 PM PDT by chasio649
World is losing its masculinity Sep 25 2002
MEN are slowly heading for extinction as the chromosome that determines their sex erodes away, some scientists believe.
To more extreme feminists, it might seem a cause for celebration. But before they start the party they perhaps should consider that the end of man could also mean the end of humankind.
Alternatively humans could split into several different species, each unable to have children with the other.
The story began 300 million years ago, long before the dinosaurs ruled the Earth, with the appearance of the Y chromosome that causes around half the human race to be born male.
Chromosomes are bundled strands of DNA along which are situated the chemical elements of genes.
At the start, the Y chromosome had a fine collection of something like 1,500 genes. But their numbers have been dwindling ever since.
Today, the Y is a shadow of its former self, and only 40 or so genes remain.
New research suggests that in five to 10 million years even those genes will disappear, and the Y will be no more.
When that happens, humanity will lose its male half. To survive, the human race will have to evolve a new way to maintain the different sexes.
Most of our genes are stored in 22 pairs of regular chromosomes, one of each pair contributed by our father and one by our mother.
But we also have two pairs chromosomes that determine our sex. In the case of women, both chromosomes in the pair are identical, but in men they are not. If both members of a pair are X chromosomes, you are born a girl. If one is an X and the other a Y, you are male.
A mother will always pass an X chromosome on to her offspring, but a father can pass on either an X or a Y. Only the Y chromosome contains a "switch", a gene called SRY, that makes embryos develop as males.
The system of sexual reproduction is vital for the survival of our species. It allows us to flush out genetic "parasites" and prevent harmful mutations being passed on to future generations while keeping hold of useful genes.
The two copies of each chromosome back each other up. They swap corresponding sections --a process called recombination --allowing damaged pieces of one chromosome to be replaced by intact sequences from the other.
Natural selection then eliminates unlucky offspring that inherit too many of the faulty bits. Recombination also shuffles the deck, ensuring that the next generation has a wider range of genes to help it cope with environmental challenges.
Herein lies the problem. At some point the Y chromosome lost its ability to swap genes. From then on, the Y was effectively doomed.
In the beginning there was no Y chromosome. The early ancestors of mammals probably did not use sex chromosomes. Instead environmental cues, such as temperature, probably decided if an offspring was male or female.
Some animals may even have been hermaphrodites, possessing both male and female body parts.
The early forerunner of the SRY "maleness" gene was a mutation on one of the pair chromosomes we now of as the X. That chromosome was destined to become the Y, which still contains ancient X chromosome sequences.
Unfortunately, there was a glitch. Part of the proto-Y chromosome broke off and re-attached itself upside down. Its reversed DNA sequence now no longer matched that of its partner, and so the two could not line up and swap parts any more. As time went by, at least three more sections of the Y chromosome became inverted, and recombination became almost impossible. Today, barely 5% of the Y chromosome matches up with the X.
Jennifer Marshall Graves, a geneticist at the Australian National University in Canberra, told New Scientist magazine in an article on the demise of the Y: "That's the death knell. All kinds of mutations accumulate, and they can't be gotten rid of by recombination."
Ever since the Y lost its ability to recombine it has been racking up a crippling collection of mutations that are slowly destroying the genes it carries. This is already causing problems for men. The biggest culprits are ancient virus-like DNA parasites called repetitive elements, which copy themselves numerous times over and infest a chromosome.
Repetitive elements can cause portions of the Y to be deleted, and this has rendered some men infertile. An estimated 15% of infertile men have lost a key group of sperm-manufacturing genes in this way.
The Y chromosome is made even more mutation prone because of the number of times it is copied. The DNA in a 30-year-old man's sperm has been copied about 350 times more than that in an egg.
Sounds like the same problem the Askar are having.
Who'th getting leth mathculine?
What about all the other species that use "Y" to distinguish males? Should not they all be losing masculinity at about the same rate?...
--Boris
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