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The Ancestor's Tale : Richard Dawkins

08/25/05

  11:44:50 pm, by Nimble   , 1534 words  
Categories: Reviews, Books, Science

The Ancestor's Tale : Richard Dawkins

Link: http://www.amazon.ca/exec/obidos/ASIN/0618005838/thecerealkill-20

This has got to be one of my favourite books of all time. I've read some of Dawkins' books before, such as The Blind Watchmaker, and always enjoyed them, but this book is utterly, utterly amazing.

Far from being the usual small book trying to prove one particular point, this is a grand survey, not just of life, but detailed explanations of radioactive dating, how trees of life are built, how creatures split apart into species, how bodies are built, with plenty of modern-day revelations about current creatures. All of this interspersed

Plus, it's heavy enough that you can seriously bean someone in the head with it :)

This is a pilgrimage "backwards" in time. The idea is that you can't really go "forwards", because evolution doesn't actually have a "plan". If you ran it all again, it would be different each and every time. However, we're here, and we have ancestors. Common ancestors, with every creature on earth. So if we go "backwards", then we will "meet up" with the ancestors of all other life on the planet.

I found the book full of interesting surprises. For example, that the line that led to primates actually diverged from the line that led to other mammals considerably before the dinosaurs died out, and that there was a split between the line that led to mammals and the lineage that led to dinosaurs considerably before the age of the dinosaurs. Actually, the lineage of creatures that led to the mammals was very heavily branched - and that all branches save a couple went extinct. It's sobering to think that the extreme bottleneck mammals went through could have very easily meant no mammals today.

The lineage of humans is traced back, and puts forth interesting questions about when bipedalism (standing on two legs) may have occurred. It sounds like it may have happened earlier than we would have traditionally pegged it. And what did happen during the 'great leap forward' about 35,000 years ago, when humans started to paint on walls?

There are a number of thoughts on the 'evolution of evolvability' - ways for evolution to adapt faster. Sex is definitely one of them, but could there be a drive towards separate species? Up until extremely recently, humans feared and hated different humans. Various animals may not hate each other in particular, but even slight differences, close to invisible to us, can cause animals that could otherwise interbreed to avoid each other like the plague.

We all have mothers and fathers, grandmothers and grandfathers, etc., but regardless of what kind of pedigree you have, every single gene in your body comes from a single line of parents, which can be different from that of practically any other gene.

A very weird result of this is that you can actually be more related to a monkey in some (note: some) of your genes than you are to a fellow human. Take blood groups, for example - these were 'invented' a long time ago. If you're blood type A, those particular genes relate you to plenty of other creatures of blood type A much closer than they relate you to someone of blood type B. The ultimate form of this? If you're a man, most of your Y chromosome genes are related much closer to other male animals of any sort than they are to any woman.

You get to learn a little bit about tricolor vision, and that it exists in the likes of lizards and turtles (some of them have tetracolor vision, tetra as in four!), and that mammals lost some use of that system (we could deduce from this that mammals - likely got their start as nocturnal creatures), and that we may have gotten back a third colour by virtue of a parasitic copy. There is a "parasitic" gene sequence called Alu that likes to be copied elsewhere in the gene. They can even be used for forensics. Often times, when they get copied, a little chunk of something else gets copied along. Our genes for red and green receptors are practically identical, though the blue receptor gene is considerably different, and off on another chromosome.

I was interested to find out that animals have a front and back develop by virtue of chemical gradients that are set up in the egg.

The techniques for figuring out the great "tree of life" with newer techniques is most interesting. It is extremely similar to trying to track down the pedigrees of old books, many of which were copied not-quite-perfectly. The Canterbury Tales is one such book for which over 20 variations eventually appeared.

Similarities in spelling, omissions, and word order can tell you how related two books are, but that alone doesn't tell you whether book A was copied from book B, vice versa, or whether both were copied from a book that disintegrated or is lost to us. The more related books you find, however, the better. If books A and B alter something, and books C, D and E have that something, but alter something else, that tells you more about the original book. You can apply the same approach (less effectively) to spoken and written languages, and even software.


A small digression here for one of my own funny thoughts. One thing creationists (you'll hear more about them later) are always on about is "missing links", no matter how many of them are found, and no matter how rare an event fossilization is (how many of you are planning on dying in a bog, or inside a cave, being dripped on my mineral-laden water, for example?), it's never enough. A similar thing happened with the discovery phase in the SCO lawsuit against IBM. They got all the released versions, but wanted all the interim versions as well, figuring that there "must" be a way that, between these versions, source code was stolen, integrated and somehow disappeared. The means for analysing the pedigrees of source code are pretty similar to those for the pedigree of living beings, and not a sane person in sight thought that SCO's request was reasonable. If you 'borrow' and still use source code from something, there will be measurable traces.

Anyhow, I digress... :)


One thing he points to when talking about how DNA builds creatures, and that is that it behaves like a recipe, not a blueprint. Blueprints require considerable revision if any small thing changes, but , for a sad example of my own, your bread dough will accomodate lower or higher temperatures, less or more leavening, and still be 'bread'.

Going way back, it looks like the major part of animal cells is related to the Archaea, a separate class of bacteria that include hyperthermophiles, like the ones that live in cracks in the rocks in boiling water, and that mitochondria are most closely related to the Ricksettia bacteria (of course, back then, there would have been nothing to give disease to :) )


A small digression for the less biologically nerdy folks: mitochondria [my-to-kon-dree-ah] are the 'batteries' of your cell. They take broken-down food and oxygen and give your cells ATP, which your cell can use to drive a lot of processes; it can be attached to things to give a one-use 'kick'. They have their own DNA, protein manufacturing and transcription, and resemble bacteria. Plants have them as well, though plants also have chloroplasts, which are related to algae (strange to think that plant cells are in some way 'parasites' on algae that joined them aeons ago). Here is a cool link on mitochondria dividing.


It really looks like bacteria combined forces to give us our modern cell. Nature isn't done with tricks like that, either. Mixotricha paradoxa lives in a termite's gut, helping it digest food, and it gets around, not by typical cilia (hairs) or flagella (whips), but a small army of attached spirochetes (spiral bacteria).

An interesting question raised near the end is what of the origin of life itself? Every creature on the planet shares not only DNA, but ribosomal DNA in particular. That would tend to indicate that there's an ancestor even further back. It's too bad that we have found no "outgroups", as they're called, living beings (not including viruses) that have heredity but that don't use DNA and/or ribosomes. The DNA and ribosome combination may have been so good that everything else became food. So, in the absence of such creatures, it's sheer conjecture at this point.

You'll notice over the course of the book that there are occasional pot shots at creationists, a particular brand of anti-evolutionist intent on showing that God created everything pretty much as is. One thing that angers him in particular, and I've seen it in action, is being misquoted. I've seen creationists seize upon discussions between the likes of Darwin and Gould on things like punctuated equilibrium, misconstruing every disagreement or discussion as a sign that the field is totally bogus and should be thrown away, in favour of their own ideas, of course (Kings of the False Dilemma, I sometimes say). You'll know why they're there when you see them :)

There's just so much to see, do and think about in this book.

More highly recommended than usual :)

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