How likely is human extinction?

Mail & Guardian Online ^ | Tuesday, April 13, 2004 | Kate Ravilious

[Momaw Nadon]

Every species seems to come and go. Some last longer than others, but nothing lasts forever. Humans are a relatively recent phenomenon, jumping out of trees and striding across the land around 200 000 years ago. Will we persist for many millions of years to come, or are we headed for an evolutionary makeover, or even extinction?

According to Reinhard Stindl, of the Institute of Medical Biology in Vienna, the answer to this question could lie at the tips of our chromosomes. In a controversial new theory he suggests that all eukaryotic species (everything except bacteria and algae) have an evolutionary "clock" that ticks through generations, counting down to an eventual extinction date. This clock might help to explain some of the more puzzling aspects of evolution, but it also overturns current thinking and even questions the orthodoxy of Darwin's natural selection.

For over 100 years, scientists have grappled with the cause of "background" extinction. Mass extinction events, like the wiping out of dinosaurs 65m years ago, are impressive and dramatic, but account for only around 4% of now extinct species. The majority slip away quietly and without any fanfare. Over 99% of all the species that ever lived on Earth have already passed on, so what happened to the species that weren't annihilated during mass extinction events?

Charles Darwin proposed that evolution is controlled by "survival of the fittest". Current natural selection models imply that evolution is a slow and steady process, with continuous genetic mutations leading to new species that find a niche to live in, or die. But digging through the layers of rock, palaeontologists have found that evolution seems to go in fits and starts. Most species seem to have long stable periods followed by a burst of change: not the slow, steady process predicted by natural selection. Originally scientists attributed this jagged pattern to the imperfections of the fossil record. But in recent years more detailed studies have backed up the idea that evolution proceeds in fits and starts.

The quiet periods in the fossil record where evolution seems to stagnate are a big problem for natural selection: evolution can't just switch on and off. Over 20 years ago the late Stephen Jay Gould suggested internal genetic mechanisms could regulate these quiet evolutionary periods but until now no-one could explain how it would work.

Stindl argues that the protective caps on the end of chromosomes, called telomeres, provide the answer. Like plastic tips on the end of shoelaces, all eukaryotic species have telomeres on the end of their chromosomes to prevent instability. However, cells seem to struggle to copy telomeres properly when they divide, and very gradually the telomeres become shorter.

Stindl's idea is that there is also a tiny loss of telomere length between each generations, mirroring the individual ageing process.

Once a telomere becomes critically short it causes diseases related to chromosomal instability, or limited tissue regeneration, such as cancer and immunodeficiency. "The shortening of telomeres between generations means that eventually the telomeres become critically short for a particular species, causing outbreaks of disease and finally a population crash," says Stindl. "It could explain the disappearance of a seemingly successful species, like Neanderthal man, with no need for external factors such as climate change."

After a population crash there are likely to be isolated groups remaining. Stindl postulates that inbreeding within these groups could "reset" the species clock, elongating telomeres and potentially starting a new species. Studies on mice provide strong evidence to support this. "Established strains of lab mice have exceptionally long telomeres compared to those in wild mice, their ancestors," says Stindl. "Those strains of lab mice were inbred intensively from a small population."

Current estimates suggest telomeres shorten only a tiny amount between each generation, taking thousands of generations to erode to a critical level. Many species can remain stable for tens to hundreds of thousands of years, creating long flat periods in evolution, when nothing much seems to happen.

Telomere erosion is a compelling theory, helping to explain some of the more mysterious patterns in evolution and extinction. There are few data - partly because telomeres are tiny and difficult to measure - but new DNA sequencing techniques could soon change that. Studies have already shown a huge variation in telomere length between different species.

Other scientists are going to take some convincing. David Jablonski, a palaeontologist from the University of Chicago, says: "The telomere hypothesis is interesting, but must be tested against factors like geographic extent, or population size and variability, that have already been proven effective in predicting extinction risk."

Stindl accepts that more experiments need to be done to test his ideas. "We need to compare average telomere lengths between endangered species and current successful species," he says. "I don't expect all endangered species to have short telomeres, since there are clearly other extinction mechanisms resulting from human threats to ecosystems, but I would expect some correlation between extinction risk and telomere length."

If Stindl is correct it will have interesting implications for mankind. Although inbreeding seems to have been the traditional way of lengthening telomeres, there could be a less drastic alternative. Stindl believes that it may be possible to elongate telomeres by increasing the activity of the enzyme telomerase in the embryo. So humans could perhaps boost biodiversity and save endangered species simply by elongating their telomeres. We may even be able to save ourselves when our own telomeres become critically short, making humans the first species to take hold of destiny and prevent their own extinction.

Indicators for human extinction Human telomeres are already relatively short. Are we likely to become extinct soon?

Cancer: Cancer incidence does seem to have increased, but it is hard to say whether this is due to longer lifespans, more pollution, or telomere erosion. The shortest telomere in humans occurs on the short arm of chromosome 17; most human cancers are affected by the loss of a tumour suppressor gene on this chromosome.

Immunodeficiency: Symptoms of an impaired immune system (like those seen in the Aids patients or the elderly) are related to telomere erosion through immune cells being unable to regenerate. Young people starting to suffer more from diseases caused by an impaired immune system might be a result of telomere shortening between generations.

Heart attacks and strokes: Vascular disease could be caused by cells lining blood vessels being unable to replace themselves - a potential symptom of telomere erosion.

Sperm counts: Reduction in male sperm count (the jury is still out on whether this is the case) may indicate severe telomere erosion, but other causes are possible.

[blam]

"What do think about that?"

Something You Didn't Know About The Cajuns (Islenos, Canary Islands)

[blam]

'Arlington Springs Woman', 13,000 Year Old Human Skeleton, California Island

[Dimensio]

So, um, some hydrogen atoms decided they wanted to become human beings one day, huh?

No. That you state the argument in this ridiculous fashion indicates that you haven't a clue as to how to go about refuting the actual science.

I never knew that conservative America was made up of so many people who are so desperate to deny God that they stoop to elaborate, unprovable, inimitable and riciculous theories.

Deny which "God"? A god of the ancient Greeks? One of the Hindu gods? Maybe a God of some Native American culture?

Oh, wait, you think that it's all about your god. You're so arrogant that you can't get past the fact that it is not about you and it is not about your religion. It's about the best explanation to fit observed evidence. When it contradicts your cherished religious beliefs, it is not -- contrary to your inaccurate assessment -- an attempt to turn people away from religion but rather a consequence of your beliefs not matching up with observed reality.

Your religion is not so important that people are working to "invent" theories to overturn it. Get over it.

As complex as the ecology and biology of this planet is, there had to be intelligence involved in it's creation.

"Had to"? That's not a very detailed assessment. Could you perhaps offer a little more detail in your conclusion?

When scientists in a lab can incite hydrogen atoms to become, oh, let's say a functioning human eyeball, or even grow one measly hair in a pertri dish,

Another strawman.

then I may lend some credibility to such atheistic drivel.

And yet another exposure of your ignorance. Hint: It's not a dichotomy between rigid Biblical litieralism and nihilistic atheism. Hypothesis on the origin of the cosmos, origin of life and the theory of evolution are not inherently atheistic. Only the ignorant claim as much.

Until then I'll just sit back and marvel at some people's inability to accept the idea of a power greater than the human mind can comprehend.

I can accept a power greater than my mind can comprehend. I just have, thus far, not seen any reason to believe that any such power exists, let alone believe that it has a very specific set of attributes and that a very specific history can be ascribed to it. "The universe is complex", btw, is not sufficient evidence to lead me to believe in the existence of such a power and even if it were, it certainly would not imply that this "power" has behaved exactly as you would have be believe (presumably as depicted from a literal reading of Genesis).

God created this world as it is in six days time, and God will decide when it ends.

Evidence for this assertion?

Judging by the posts on this thread, some of you had better fear that day.

Your inane and veiled threat (you'll find out I'm right someday, just wait and see, and then you'll regret not believing me!) is duly noted.

[PatrickHenry]

They're gonna get you!

[Dimensio]

Ah-hah! Your slip up posting of that image PROVES without ANY DOUBT that you are actually a member of the Illuminati!

[NorthWoody]

Throw around all the insults and condescension you can muster, there Mr. Einstein, I can play that game too.

As far as the Carlinesque questions as to whether my God is "better" than the Hindu god, or the Buddhist god, I can only believe that the God to whom I pray is the One True God, Father, Son and Holy Spirit. Or, for those who prefer a little reverent humor, as I'm sure God himself does from time to time, they can be referred to as Big Daddy G, Junior J and The Spook. :) Christianity stems from the Holy Land events as recorded in the Bible. Whence cometh the beliefs of other religions, I do not know much about that, nor do I care.

My evidence to support God creating the world is in the Holy Bible, book of Genesis. "In the beginning, the earth was without form, and void, and the spirit of God moved upon the waters..." I see no need to spend time, sweat and money trying to prove or disprove that which cannot be proven or disproven. That is the job of those who fear death and what awaits them in the hereafter so much that the must attempt to assuage their trepidation through meaningless junk science.

The clincher here is this, if I'm correct in my belief in the book of Genesis, I'll be spending eternity in a field of clover with a cold drink right there whenever I reach for it. Meanwhile, you and your buddies will be stoking a furnace while Asmodeus, Judas Iscariot and Adolf Hitler take turns jabbing you in the glutei with a trident should you stop shoveling for a moment to wipe your brow.

If you're correct in your belief that science holds the key to how our universe originated, then neither of us will ever know it. Death will be the end of all our thoughts, and all things will over and done with for us.

I'll stay with my line of thought. It suits me better. Thanks for your interest.

[Dimensio]

Throw around all the insults and condescension you can muster, there Mr. Einstein, I can play that game too.

I've no doubt of that, though it doesn't impress me. I'd actually be impressed if you could actually support your claims with evidence and refute the relvant science rather than appealing to bogus strawmen and lying about the purpose of science.

As far as the Carlinesque questions as to whether my God is "better" than the Hindu god, or the Buddhist god, I can only believe that the God to whom I pray is the One True God, Father, Son and Holy Spirit.

I never asked whether your good was "better". I merely pointed out that you arrogantly assume that a cabal is out to get you and your god, over all others, when they propose hypothesis or theories that contradict your literal interpretation of a single religious text.

Christianity stems from the Holy Land events as recorded in the Bible.

Please tell me something that I don't know.

Whence cometh the beliefs of other religions, I do not know much about that, nor do I care.

Yes, that was my point. You can't seem to get it through your head that your personal religious beliefs are special to you only. They are not special to me (a non-believer) and they are not special to the scientists who are deriving conclusions that contradict your literal interpretation of religious "history" -- and as such they are not out to "disprove" your religion.

My evidence to support God creating the world is in the Holy Bible, book of Genesis. "In the beginning, the earth was without form, and void, and the spirit of God moved upon the waters..." I see no need to spend time, sweat and money trying to prove or disprove that which cannot be proven or disproven.

In other words, your "evidence" is your assertion that the specific words of a single religious text are literally true, but you have absolutely no evidence to offer to show that they are, in fact, literally true.

That means that you don't have any evidence. Dressing up an unsupported assertion and calling it "evidence" doesn't make it so.

That is the job of those who fear death and what awaits them in the hereafter so much that the must attempt to assuage their trepidation through meaningless junk science.

And here you demonstrate that you have utterly ignored my previous point, thus showing me that you choose to be ignorant of the facts, and that you would rather libel the nature of science than try to understand it. I do hope that you're happy wallowing in your willful ignorance.

One more time, just in case you ever wish to bring yourself into reality: science is NOT about disproving your particular religious beliefs. Science is about the study of the natural universe. When the conclusions of scientists contradict your religious beliefs, it is because that is what is best derived from their observations of reality, it is NOT, despite your incredible arrogance, an attempt to disprove your religion for fear of some horrors in an afterlife.

The clincher here is this, if I'm correct in my belief in the book of Genesis, I'll be spending eternity in a field of clover with a cold drink right there whenever I reach for it. Meanwhile, you and your buddies will be stoking a furnace while Asmodeus, Judas Iscariot and Adolf Hitler take turns jabbing you in the glutei with a trident should you stop shoveling for a moment to wipe your brow.

If you're correct in your belief that science holds the key to how our universe originated, then neither of us will ever know it. Death will be the end of all our thoughts, and all things will over and done with for us.

And if the Muslims are right, then we're both screwed. And if there exists a god who prefers scientists and rationalists over religious zealots, then I have paradise awaiting me and you'll be the one facing eternal torment.

Pascal's wager is a worthless argument, relying upon the fallacy of the false dilemma. That you use it indicates that you've given absolutely no thought whatsoever to the subject at hand.

I'll once again point out that you have fallaciously equated evolution with atheism. Evolution != atheism. Once again, you are incredibly ignorant (or dishonest) to make such a claim. Not everyone who accepts evolution as a realistic scientific theory is an atheist. There are those who believe that evolution is true and that a god exists.

[balrog666]

I can only believe that the God to whom I pray is the One True God,

Some muslims make the same idiotic claim. So do some Hindus. So do some stupid and bigoted adherents of every other religion.

When you guys work out who is correct, let us know.

[arielb]

Extinction is very likely unless we do something about Global Warming which is accepted as fact by a consensus of practically every scientist in the field

[Long Cut]

Sigh.

What is so hard to understand about "Evolution is the theory which best explains the available data?"

Or, "Evolution makes no claims as to the origins of life, it only discusses the changes in species over time"?

[F.J. Mitchell]

The race of humanity toward extinction has been greatly enhanced by inbreeding between humans and lemmings.

[PatrickHenry]

What is so hard to understand about "Evolution is the theory which best explains the available data?"

Nothing. That is .. unless you already know the truth^tm, which is that evolution is a Satanic cult, the only purpose of which is to deny God, and all the eee-voo-louuu-shunist evidence is fake. Then, armed with the truth^tm, one can properly deal with (i.e., ignore) the pathetic lies of the evil ones.

[Long Cut]

I grasped the Scientific method pretty well back in the 7th grade...it's easy:

1. Observe a phenomenon;
2. Collect all available physical data regarding said phenomenon;
3. Formulate theory to explain said phenomenon, within available data;
4. Make predictions based upon the above;
5. Perform experiments to verify predictions;
6. If additional evidence becomes available which invalidates the theory, discard or modify as necessary to fit the new data;

Why do so many people fail to understand this?

[I got the rope]

ROTLMAO!...that was very f.christianesk of you Patrick.

[bondserv]

Great link and post.

[bondserv]

Nothing. That is .. unless you already know the truthtm, which is that evolution is a Satanic cult, the only purpose of which is to deny God, and all the eee-voo-louuu-shunist evidence is fake.

Then, armed with the truthtm, one can properly deal with (i.e., ignore) the pathetic lies of the evil ones.

The truth^tm requires some scripture verses to be posted.

Must I always instruct you my young padawan.

I knew you loved us!

[Ken H]

History trivia-- Charles Darwin began burning in hell forever and ever on this date, April 19, in 1882.

Benjamen Disraeli and Pope Leo IX also died on April 19 of 1881 and 1054 respectively.

I'm not sure if they're being barbequed or not.

[null and void]

They missed 7th grade?

[capitan_refugio]

"Arlington Springs Woman"

That's the one!

[capitan_refugio]

An opportunity to revive another old thread! I was fascinated by the "Canary Island Pyramid." The masonry was impressive, especially for a "stone age" population.

However, that thread and what has been posted on this one makes me think that the idea of Canary Island Neanderthals is probably far-fetched.