How likely is human extinction?

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.

[Would you care to try another creationist misrepresentation, or are you going to be wise enough to stop here?]

Wait a second. It's the evolutionists who came up with their unprovable (meaning neither measurable, observable, nor repeatable) and ever-evolving theory as a way to kill God.

Wow, I guess the creationist misrepresentations *aren't* going to stop.

Sorry, but you're very mistaken and/or misinformed. First, evolution is indeed measurable, observable, and repeatable. You've been reading too many creationist screeds about evolution and not enough science.

Second, evolution is not "ever evolving", at least not in the sense you mean it. The basics of the theory of evolution are unchanged from Darwin's original concepts.

Finally, evolution was not "come up with" as "a way to kill God". That notion is just false, bizarre, and more than a bit paranoid. Evolution was developed as a way to best explain the evidence. That's what makes it one of those "scientific theory" things you must have heard about between revival meetings.

Therefore, it is the consistent evolutionist, having no fear of God,

How do the millions of Christian evolutionists fit into your tidy little oversimplistic view? Or did I just make your head explode?

who would have the greater propensity to lie and deceive, insofar as his atheistic world is, well, atheistic

Not that I've noticed, frankly.

(I won't bother here with theistic evolution as it is a farce).

There are millions of Christians who disagree with you on that. And you can't make the obvious hole (e.g. many evolutionists are Christian) in your ridiculous premise ("evolutionists are atheists") go away just by declaring that you "won't bother with" it. Not if you want to avoid being laughed at, I mean.

The creationist holds his views in a theistic framework guided by principles like honesty, as codified in the Ninth Commandment.

In theory, anyway. There are any number of obvious exceptions.

Your charge lacks both consistency and intellectual honesty,

Okay, let me get this straight -- your argument is that "'fits and starts' defy traditional evolutionary thought" can't possibly be a misrepresentation because it's simply not possible for creationists to make a misrepresentation? *And* that evolutionist must obviously be lying if they say that it is because they're all godless heathens with nothing them stopping them from lying?

Go ahead, pull the other leg know.

Or at least proofread your posts for ludicrousness before you send them.

But hey, son, just to demonstrate how your "masterful" armchair ehtical analysis turns out to be dead flat wrong somehow, let me provide black-and-white proof that "fits and starts" are *indeed* part of "traditional evolutionary thought", and do not "defy" it as some creationist misrepresented the case, by quoting the most "traditional evolutionary thought" of all (Darwin's original book on evolution) where he was quite clearly talking about evolution proceeding in "fits and starts":

I further believe that these slow, intermittent results accord well with what geology tells us of the rate and manner at which the inhabitants of the world have changed." (Darwin, Ch. 4, "Natural Selection," pp. 140-141)
But I must here remark that I do not suppose that the process ever goes on so regularly as is represented in the diagram, though in itself made somewhat irregular, nor that it goes on continuously; it is far more probable that each form remains for long periods unaltered, and then again undergoes modification. (Darwin, Ch. 4, "Natural Selection," pp. 152)
"It is a more important consideration ... that the period during which each species underwent modification, though long as measured by years, was probably short in comparison with that during which it remained without undergoing any change." (Darwin, Ch. 10, "On the imperfection of the geological record," p. 428)
"Widely ranging species vary most, and varieties are often at first local, -- both causes rendering the discovery of intermediate links less likely. Local varieties will not spread into other and distant regions until they are considerably modified and improved; and when they do spread, if discovered in a geological formation, they will appear as if suddenly created there, and will be simply classed as new species. [Charles Darwin, Origin of Species 1st Edition 1859, p.439]
[All quotes from Darwin's 1859 "On the Origin of Species"]

This is classic Punctuated Equilibrium -- from Charles Darwin in 1859.

Evolution by "fits and starts" is *indeed* part of "traditional evolutionary thought". QED. And any creationist who claims otherwise is engaging in misrepresentation.

So the next time you're tempted to jerk that knee and fall into the all too common creationist mindset of, "anything a creationist says must be right and anything an evolutionist says must be a lie", remember that sooner or later it's wise to actually do a reality check and FIND OUT which side happens to be correct on any given point.

It's also worth noting that the whole purpose of the scientific method is to make sure you *do* reality checks (that's what experiments etc. are all about), while the pitfall of Faith (with a capital "F") is that it can lead you to believe that you don't *need* to do any reality checks in the things you have Faith about (indeed, the notion is often that one should *discard* any reality checks that happen to contradict the Faith, as they are devilish tricks and temptations).

Faith can be a wonderful thing, but the wise man realizes that it can at times be mistaken. Believing in something hard enough (like the alleged infallibility of creationists on science matters) doesn't make it automatically true.

....the law of the excluded middle is no longer valid. Something in the nature of atoms must allow the development of consciousness, otherwise how would our material beings have consciousness?

Only if one presupposes that matter precedes Mind. Post hoc ergo propter hoc - BECAUSE we have consciousness SOMETHING IN ATOMS MUST ALLOW the development of consciousness?

Why the MUST? What other possibilities are there besides the atoms being the source of conscsiousness? Just because one cannot think of other possibilities does not mean that such possibilities do not exist.

Also - DEVELOPMENT - the assumption that consciousness DEVELOPS - i.e. it is not a SUDDEN thing that happens as a result of imputation from the outside of the material universe is an arbitrary presupposition and seems to come from the hope that there is no Designer outside the material realm.

Going back in time, under the assumption that energy and/or matter or something was once condensed into a tiny tiny place and then exploded, one must argue that the explosion contained the building blocks of consciousness - i.e. the tiny compressed universe itself was not aware of itself but the explosive creativity of that moment resulted in matter hurling thorugh space at all kinds of angles and directions (and by the way where did this 'space' come from?) and then gradually atoms assembled together in such a way that eventually a 'person' with consciousness existed and now could comprehend the fact that his consciousness is just a wierd quirk of no relevance to any plan or purpose, and that ALL his thoughts and propositions are nothing more than the result of cause and effect train of purely physical, chemical forces.

Cordially,

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