EPS Review #214 - The Ancestor's Tale

The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution , by Richard Dawkins, Phoenix 2004, 685pp.

Ewan had this huge cladogram printed up for the office walls. As we geekily pored over it, I asked a lot of questions like "shouldn't there be more bacteria?" and "why are the fungi at the end?", which resulted in Ewan pressing The Ancestor's Tale into my hands the next day. He loves Dawkins, but this is the first I have read.

If you see the word 'No' then you are colorblind There is a lot of great stuff in this book. Dawkins points out that DNA is like a huge textual stemma, which is sort of obvious but still a very appealing analogy to a philologist. He leads from examining alternate texts of Chaucer to explaining how biologists estimate distances between species in order to place them on the correct branches of the family tree. There are loads interesting results from DNA tree work, such as that the hippo appears to be the closest relative of the whales.

When contemplating my genealogical obsession I got to thinking that it must counter-intuitively be possible to have an ancestor from whom you have inherited no genetic material, and Dawkins confirms this on page 47. In fact he points out that it makes much more sense to follow the genealogy of genes than of individuals.

I loved the section on color blindness. My dad is color blind, and I kind of knew that these genes are on the X chromosome. So men are more often color blind than women are. This isn't necessarily an evolutionary disadvantage: Dawkins cites stories about WWII bombing crews wanting color-blind spotters aboard because they could notice camouflage more easily (if the image link at the right is working, we trichromats should see nothing, but indeed my father sees a short word ). Three color vision probably derived from gene duplication from a messy meiosis -- then the duplicate gene evolved such that its protein's peak sensitivity was at a different frequency. The obvious conjecture is that there much be some tetrachromat humans around, probably female. Imagine having four-dimensional color vision! Cool.

Another great morsel for thought is that evolution is hugely faster than geological time. Darwin finches can be shown to evolve significantly after just a few seasons of extreme weather. So the fossil record will always be missing a lot of interesting variation and any number of "missing links".

As for the always-interesting topic of why humans are so hairless, if you believe that it relates to the invention of clothes then, by estimating the divergence of the human body louse and head louse DNA over time, some German scientists place the invention of clothes to be 72,000 +/- 42,000 years ago. Cooool.

"If you take blood and compare protein molecules, or if you sequence genes themselves, you will find that there is less difference between any two humans living anywhere in the world than there is between two African chimpanzees. We can explain this human uniformity by guessing that our ancestors, but not the chimpanzees', passed through a genetic bottleneck not very long ago. [...] There is evidence of a fierce bottleneck -- perhaps down to a population of 15,000, some 70,000 years ago, caused by a six-year "volcanic winter" followed by a thousand-year ice age." Fascinating. Dawkins is not afraid to go on to make comments about our perception of race, despite our minuscule genetic variation.

In fact, I may as well say here that Dawkins is not afraid to yammer on and on about all sorts of topics. I felt like he wrote this book by speaking into a Dictaphone and loving the sound of his voice. Not only does he explain carbon dating in detail, but he even starts that explanation with a prefatory explanation of what an atom is. Who does he think is reading this book? Even children know what atoms are. I know the answer: he thinks creationists are reading this book. And I suppose he should know. You would think the sheer mass of exquisite and consistent scientific detail in this book alone would convert a creationist, but I suppose that assumes that creationists are capable of thought. Anyway, the book is way too long and wordy.

The mixotrich borrows other microbes Another reason the book felt long is that I was eager to hurry past the cute animals (the story framework is a reverse-time peregrination up the family tree) and get to the earliest life forms. One of the coolest microbes is the mixotrich which lives in the gut of a termite. It uses spirochaetes as cilia! Incorporating microbes into our very cells is a trick that all we eukaryotes have pulled off. It's just amazing.

tree of life I was just in an Oxfam shop and found a huge hardback copy of this book for only £5! It is chock full of plates and diagrams, much nicer than the paperback I read. I'm going to leave it in Ross's room, since he is keen on DNA. It's an amazing molecule.

Mark wrote: I did enjoy this review and certainly your comment on creationists. Remember faith requires simple belief even in the face of facts that simply contradict ones faith. We humans as an odd bunch.

Carl wrote: Interesting.

I rendered the dot thing in gray scale, and I still don't see anything. I must have the fourth color syndrome. What is the word hidden in those little dottskies?

I have entertained the preposterous notion that our lack of hair meant that the human ancestor was once water-going. Besides the lack of hair (except the long hair on Mom and Dad's head so the babies could cling), there is the subcutaneous fat to help keep out the cold, the extra fat on the breasts so they would be buoyant, the rapid adaptation we have when jumping into cool water, the fact that we can hold our breath (can other land mammals do that?) Also there is our fascination with the seaside.

Sorry, I forget all the references.

I replied: The web page that hosts the image lets you apply a red-green filter (for some reason, this takes a huge amount of time), and then you can see that the word is "No". Like the Dr. perhaps.

Yes, I have heard the aquatic ape theory on the lack of hair. OTOH, seals have hair worth clubbing them over. So maybe we were somewhere nice and warm, like the Maldives.

Ewan wrote: Glad you liked it but yes, it is overly long. Like many of Dawkins' later books, you feel like saying "Enough already...I've got it...don't go on and on about it".

True also about rushing through the cuddly things to get to the really interesting stuff way way back in time. I did the same thing. Bored with monkeys, want to know about archea...

Kevin wrote: The women tetrachromats thing is interesting. I was just coincidentally looking at this as a digression from my MCAT studies. This paper suggests that maybe half of all women are tetrachromats. I swear Elise is! I had theorized her amazing color acuity was due to a greater ratio of cones to rods, but the tetrachromancy makes more sense.

I just read Born to Run. You know how I love best sellers. I bet you would like it, too--motivates you to run more, has an entertaining story, and some interesting science. It's also comforting that we, at 50, should be running faster than when we were 19.