The Greatest Show On Earth by Richard Dawkins: CHAPTER 5 'Before Our Very Eyes'
Try to imagine variations without limits!
In this chapter RD tells us about some interesting experiments that “serve beautifully to illustrate the speed with which natural selection can go to work.”
RD illustrates the power and beauty of natural selection by the use of several graphs, and by the use of organisms as diverse as bacterium and elephants.
Elephants.
He starts with an example of what he says is natural selection at work in elephant tusks.
He uses a graph to illustrate the downward trend in tusks in Ugandan elephants.
“We must seriously entertain the possibility that it is a true evolutionary trend, in which case it is a remarkably rapid one...We seem to have prima facie case of rapid evolution taking place before our very eyes.” p113
Firstly, if we examine the graph which covers about 35 years of data, but looking closely we discover the years are 1925-1960. The graph is not from any ‘scientific study’ but it is taken from the Uganda Game Department of 1962. Apart from the fact that the graph is almost 50 years old, there is no follow up data, on how things have progressed since then. He does admit that this may require ‘further research’, though he does not mention if there has been any carried out.
If we examine the information in the graph: the vertical axis, only tells us the weight of the tusks, and the horizontal axis, only tells us the year. So the graph only shows a downward trend of the weight of the tusks of animals shot by the Uganda Game Department over a 33 year period. This hardly seems to be sufficient information to base a ‘scientific study’ on, as we do not have other information which may be relevant. We do not know what age the elephants were, or their size or the status of their health, or even why they were shot. It would seem that these things could effect the outcome of any ‘scientific analysis’, but instead he is happy to draw his conclusions on a ‘dated’ graph, which has no additional follow up study in the intervening years since 1960.
“The fact that there is a statistically significant trend towards shrinking tusks doesn’t necessarily mean it is an evolutionary trend” p112
“We must be cautious before concluding too much” p113
Nonetheless he tells us:
“I am inclined to take seriously the possibility that it is a true evolutionary trend” p113
Of course, maybe this should not surprise us, since he is an evolutionary biologist, he is ‘likely to see such trends’ and take them seriously.
There was an interesting sentence within this example, considering his opinions on ‘examining the evidence’.
“It could be that we are observing strong natural selection which is likely to result in changes in gene frequencies in the population, but such genetic effects have not so far been demonstrated” p113
(Emphasis added)
So the graph is dated, there is no follow-up ‘scientific study’ and the even the graphs results are open to questions. So, why does he think this is a “true evolutionary trend”?
Well, his friend and “world authority on wild African elephant populations, takes it seriously”. Would this be what some may call an ‘appeal to authority’, even if it is a ‘world authority’?
Anyway, if we simply ignore all these problems, and accept his conclusions as accurate, what does his example show? All it actually shows is that it is ‘possible’ that the tusks of elephants have become smaller, in the time period of the graph. It does not show what factors have contributed to the reduction in size, or if the trend has continued past 1960.
Lizards
His next example is of 2 species of lizards, which live on Mediterranean islands.
One of the island groups is transported to another island, and his example tells us what happened to them. Some scientists went to the island 37 years later and found that ‘apparently’ “the ‘evolved’ population – had significantly larger heads than the ‘original’ Pod Kopiste population: (transported lizards) longer, wider and taller heads. This translates into a markedly greater bite force. A change of this kind typically goes with a shift to a more vegetarian diet... the lizards...eat significantly more plant material than the ancestral type...” p114
Once again there are assumptions made, but if we accept that they are correct, what does this example tell us?
This example shows us that lizards have some variations from the original lizards which were transported there 37 years before. They have ‘adapted’ to the new environment, and have modified their eating habits, to accommodate the food sources on the island.
The lizards showed a variation from the normal head size, and got larger heads.
The lizards did eat plants before; they simple eat ‘more’ of them. This is an example of ‘natural selection’ favouring those ‘best suited to the environment’.
In this section RD tells us that “our appendix is a vestige of the larger caecum in our more vegetarian ancestors”. Of course, as is typical in this book, he offers no evidence to back up this assertion, and it is also interesting that he does not actually claim that the appendix is a ‘vestigial organ’, as no doubt he is aware that recent research has show that the appendix is not the useless organ that it was once thought to be. The appendix is now no longer thought to be useless, but along with a list of other organs that were once thought to be useless, it now turns out to have a use.
http://www.livescience.com/health/090824-appendix-evolution.html
After telling us this, he then says;
“although caecal valves don’t normally occur in (these lizards)..., those valves have actually started to evolve...” p116
Once again, he offers no evidence for this, and I am not sure how he knows they have ‘started to evolve’ and he does not tell us this. It would be far better to have quoted the original paper of this study, to let us see how the authors formed their opinion, but alas, he does not do this, but simply puts a ‘chapter note’ at the end of the book which lists the names of the authors. This means that we have to rely on RD account of the events, and this can hardly be quoted as ‘evidence’
The next example, is the main feature of the chapter, and arguably one of the only ‘real science’ experiments and best ‘evidence’ of the book, but I will come back to that in a moment and move on to a couple of other examples first.
Guppies and ‘living fossils’
Rather than go over all the details of this ‘experiment’ I will simply get straight to the results of it, which in RD words “They were spectacular”.
The guppies in this ‘experiment’ “matured at a later age...and they produced fewer and larger offspring”, and there was a number of variations of the size and number of spots on the guppies. Again, this is said that “It is a spectacular example of evolution before our very eyes.”
I don’t know if I would class these results as “spectacular” but I would agree it is another nice example of ‘adaptation to a particular environment’.
After discussing the “evolution before our eyes”, he then discusses his favourite ‘living fossil’ the brachiopod Lingula, which he says “have changed so little that they might almost interbreed with their remote ancestors”.
“Many of the problems that we meet in evolutionary argumentation arise only because animals are inconsiderate enough to evolve at different rates, and might even be inconsiderate enough not to evolve at all.” p141
The reason he admits that some animals don’t “evolve at all” is because Lingula is so similar to fossils from ‘450 million years ago’.
I must admit I find this interesting, in light of what the rest of the chapter is trying to convince us of, i.e. the speed of change in many different organisms. Yet, in this case, and in others too, we are supposed to ‘believe’ that for 450 million years, instead of the vast amounts of ‘mutations’ that have changed fish to people in the same period, so few ‘mutations’ have effected Lingula in 450 million years that it remains “almost wholly unchanged”. Whilst we are told that it is random mutations that drive evolution, we are now told that in some organisms there have had so few ‘random mutations’ that a living species is so similar to one that is ‘450 million years old’ “that they might almost interbreed with their remote ancestors”. On this subject though, he does make another interesting observation;
“I must admit, however, that a fossilized shell is not a lot to go on, and some zoologists dispute Lingula’s claim to be an almost wholly unchanged ‘living fossil’.” p140
It appears that he is saying, that though he has an opinion on this ‘living fossil’, his opinion is not unanimous, and others disagree, as the ‘fossil record’ is not that easy to interpret accurately. I would agree, and wonder what definition can be used to identify ‘species’ of fossils, when they have no knowledge about it ‘breeding’, or ability to interbreed.
Anyway, these examples of ‘fast’ and ‘slow’ evolution are only the supporting features, the main feature of this chapter, is one of the only real ‘scientific experiments’ described in the whole book. The experiment is a long term one, carried out by Richard Lenski on the bacterium Escherichia coli or just E.coli to most of us.
RD spends many pages describing this experiment, which along with being a very interesting one, it appears to be a well thought out, and executed one. Rather than go over all the details he gives, you can check out an overview at http://en.wikipedia.org/wiki/E._coli_long-term_evolution_experiment
Briefly, this experiment covers 20 years worth of data, in which 45,000 generations of E.coli were produced in 7000 different flasks in batches of 12, in what RD describes as “sort of like the twelve tribes of Israel”. Each day about 100th of each of the 12 tribes were carried forward in a glass “Noah’s ark”. RD does love his biblical references.
The experiment covers about 45,000 bacterial generations and;
“To put that into perspective, if we were to go back 45,000 human generations, that would be about a million years, back to the time of Homo erectus”
So this experiment is an illustration of 1 million years worth of “human generations”, and RD takes particular pleasure in telling us that the results of this experiment “are distressing to creationists, for very good reason. They are a beautiful demonstration of evolution in action, something it is very hard to laugh off even when your motivation to do so is very strong. And the motivation for dye-in-the-wool creationists is very strong indeed” P117
I guess I would probably fall into RD category of a “dye-in-the-wool creationist”, so I would imagine the results of this experiment are supposed to be “distressing” to me.
So, what are the results of this experiment which were carried out in “perfect perfect perfect conditions for evolution”?
“In all twelve tribes the average fitness increased as the thousands of generations went by. All twelve lines got better at surviving in these glucose-limited conditions... and the average body size of the bacteria grew, in all twelve lines." p122
So, they took bacteria, put it into a particular environment, and watched as each generation ‘adapted’ to this environment, and over time all 12 lines grew in body size, and became better at surviving in the limited environment. This hardly seems like anything that should be devastating to creationist!
“What this evolutionary change suggests is that becoming larger is, for some reason, a good idea when you are struggling to survive in this alternating glucose-rich/glucose poor environment. I won’t speculate on why increasing body size may be an advantage- there are many possibilities- but it looks like it must be so, because all twelve did it.” p124
It is interesting that in a book filled with RD “speculations”, he decides on this occasion to say, it must be better, because they all do it.
“But perhaps even more interesting is that sometimes a pair of tribes seem to have independently discovered the same way of getting bigger... looking at their DNA. The astonishing result they found was that 59 genes had changed their levels of expression in both tribes, and all 59 had changed in the same direction. Were it not for natural selection such independent parallelism in 59 genes would completely beggar belief.” p124
Perhaps RD is unaware that creationists do not deny either ‘random mutations’ or ‘natural selection’, and therefore these results are not as surprising or as distressing as he thinks they are. He does not give any details of what these changes were, so it is hard to comment on why he thinks it is so distressing. He comments that this result is too improbable to have happened by chance, and says of course it did not happen by chance, but by cumulative natural selection. This is not the problem to creationists that he thinks it is, as they acknowledge that both of these things can occur, it is the addition of new information which is disputed, not natural selection working on mutations.
Of course, adding new information is what RD then claims has also happened in this experiment. His claim is that one tribe “suddenly acquired the ability to eat citrate as well as glucose, rather than only glucose.”
“Was this sudden improvement in ability to draw nourishment all due to a single dramatic mutation...This seemed to Lenski unlikely...he calculated that 30,000 generations was long enough for every gene to have mutated at least once in each of the twelve lines...There was another theoretical possibility... What if the necessary biochemical wizardry to feed on citrate requires not just one mutation but two (or three)?” p128
This is an interesting statement for a number of reasons: thinking back to the example of the ‘living fossil’ which is almost the same as its ancient ancestor, how many generations would have passed in ‘450 million years’? And would this not have been sufficient time for “every gene to have mutated at least once?"
Now what RD wants us to believe is that this “theoretical possibility” has actually happened, but this experiment has not shown that to be true, it is “all hypothetical”, and rather than actually showing that this is 'actually' what has happened, this experiment has done little more than “take great strides in that direction.”
RD spent much more time on describing this experiment, than he did in giving actual data and results of the experiment, as in reality, this experiment did not ‘observe’ this “theoretical possibility” but it is only a working ‘hypothesis’ which has not yet been show to be a reality.
So once again, RD makes the ‘claim’ that new information was “acquired”, but has not presented any actual ‘scientific evidence’ that it was, but only offers speculations and hypotheses, and tries to make them out to be ‘scientific evidence’.
In describing this experiment, RD has focused on the elements which he feels gives credence to his claim, but has ignored some of the negative outcomes of the data.
Rather than showing E.coli ‘evolving’, he has given an example of bacteria ‘adapting’ to a particular environment, in a lab, and has ignored the facts that the bacteria may have ‘adapted’ to be able to gain nourishment from citrate, but in the process, they lost the ability to perform other functions. This is not out of line with the creationists point of view, as the ability to produce a vast range of variations of bacteria along with ‘natural selections’ ability to help those better suited to a different environments, is in line with what they would predict.
All organisms have a vast range of variations within the ‘species’, and there are many different variations which are better in one environment than another. The fact that ‘natural selection’ (which is not denied by the creationists) permits some variations to thrive in one environment better than others, is all that is illustrated by this experiment, those best suited to the environment in the lab thrive and survive, those not suited to it do not survive in that particular environment.
We must remember that the E.coli in this experiment were ‘artificially ‘enclosed and they may or may not survive in the ‘wild’.
What do you reckon the chances of a Pekingese surviving in the wild?
In short, this experiment showed that over the equivalent of 1 million years of human generations, E.coli got bigger and more numerous in this environment. I hardly see this as devastating to the creationist viewpoint. Bacteria are supposed to 'evolve' rapidly, yet whilst they got 'bigger' man apparently evolved to a much greater extent in the same 45000 generations.
So, though this chapter has given several illustrations of what RD calls “evolution before our very eyes”, he has used a subtle switch with the definition of ‘evolution’.
On page 17 RD told us: “the fact of evolution (all living things are cousins)”, telling us that ‘the fact of evolution’ “is our common ancestry”. But now, in this and most chapters, he changes the meaning of ‘evolution’, to that of ‘change over time’.
The ‘fact’ that organisms ‘change over time’ is not disputed by creationists, but the ‘fact’ that “all living things are cousins” is. In this chapter, RD gives illustrations of organisms changing over time, and wants to say that this is evolution. If that was the case, even the creationists would say ‘amen’ with him. This is not what this book is supposed to be about. He has claimed that ‘the fact of evolution’ is that we all have a ‘common ancestor’, all this chapter illustrates is things which even the creationist agree with, along with some of RD speculations, which they do not agree with.
To conclude this chapter, I will finish with a couple of RD quotes which illustrate the kind of ‘speculations’ he wants us to have in our mind for the rest of the book.
“Imagine if we could bring Lucy, the magnificent pre-human fossil discovered by Don Johanson, back to life…and set her kind evolving anew!” p117
“So, whatever evolutionary change Lenski may have clocked up in the equivalent of a million years of bacterial generations, think how much more evolution might happen in, say, 100 million years of mammal evolution.” p119
This chapter has given us some nice illustrations of ‘change over time’ before our eyes, but has not given us any evidence of the ‘fact’ of common ancestry.
It is interesting though, that the kind of illustrations that have been used in the past to illustrate ‘evolution before our eyes’ have not even been mentioned. There are no ‘finches’ to show ‘natural selection in action’, and the poor old peppered moths which used to be used as an example, don’t even get a mention. I would suspect that this is because RD knows that further use of these is of little use to his claim.