Dawkins is one of the more famous and respected evolutionary biologists in the world, and already has several impressive books to his credit, but this one is perhaps the best and most accessible. Taking a tip from Geoffrey Chaucer’s “The Canterbury Tales”, he depicts humans as going on a journey to locate the common ancestors they have with other groups of organisms, joining with those groups, going farther and farther back in time until they all converge with bacteria, the most primitive organisms of all. These other organisms have representatives that are described by Dawkins in “Tales” that show how they live and how they may relate to humans. Dawkins frequently refers to both the fossil record and “molecular evidence” to support his claims about the organisms featured in this book. He also invents a new term, “concestor”, which is short for “common ancestor” (Personally, I think he should have spelled that word “comancestor”, since that sounds stronger). Among other mind blowing things, we discover:
1.That the chimpanzees (and bonobos) are indeed our closest relatives. Indeed, they are more closely related to human than they are to any other ape, including gorillas and orangutans, which shows that any grouping of these apes that does not include us is inaccurate. We are merely highly modified apes and should be placed in the same family as them.
2. That the placental mammals were already diversifying long before the dinosaurs became extinct at the end of the Cretaceous, since the concestor of all of them lived over 100 million years ago.
3. The monotremes (egg laying mammals) concestor with us lived about 180 million years ago, at the beginning of the Jurassic period. Had the dinosaurs never evolved, monotremes might have inherited the earth after the Triassic terminal catastrophy and the so-called “Age of Reptiles” would have been a lot shorter and the Age of Mammals would have begun with the Jurassic instead. There would have been no birds either, since birds came from dinosaurs.
4. Speaking of birds, they are more closely related to crocodiles than to any other group of living animals. The concestor of all reptiles with all mammals lived over 300 million years ago, in the Carboniferous period.
5. There are two basic divisions of higher multicellular animals, the Protostomes and the Deuterostomes. We are of the latter group, but vastly outnumbered by the former which include insects, spiders, mollusks, and many kinds of worms. The concestor of both groups lived in Precambrian times.
6. Shockingly enough, we find that fungi, which were once considered plants by most biologists, actually are more closely related to us animals!
7. Plants rule the world even more than insects do! Indeed, without plants, none of us animals and fungi would even exist!
8. Chloroplasts and mitochondria are descended from bacteria living over a billion years ago that entered into a symbiotic relationship with larger cells, enabling the cells to photosynthesize and to breath oxygen respectively. Animals, plants and fungi all descended from the organisms that first got the mitochondria, while only the plants have the chloroplasts (unless you, like Dawkins, do not count certain protists like Euglena and diatoms as plants merely because they have chloroplasts too. This is one place where Dawkins and I strongly disagree.)
9. There are actually three “domains” of life, the Eukarya, the Archea, and the Eubacteria, that are above even the five classic kingdoms in rank, according to the molecular evidence.
10. Finally, we meet the Eubacteria, and since there is no living life form known that is more primitive than bacteria (viruses actually evolved much later as parasites on all other organisms) our journey ends. We are about 3.5 billion years in the past.
11. Were evolution to be run again on Earth from the very beginning, anything exactly like humans would not have emerged. The random character of evolution would have had millions of different species evolving, though many might resemble those we know. And that random character means that it is impossible to predict with certainty what the future of any species living today, including our own.
Yes, Dawkins is an athiest, and makes reference to his disdain for beliefs in the supernatural even in The Ancestor's Tale. But we must remember two things:
- The official position of this group is strictly neutral regarding religion, though individual members may follow different faiths or no faith at all. Those differences are never to be an issue here.
- Atheism is itself unscientific in the sense that it is impossible for an observation or experiment or any kind to support the assumption that there is no God, since you cannot prove a negative. You can only say that the burden of proof is on the beleivers in God and they have not proved their case beyond a reasonable doubt.
I think Dr. Dawkins gets so hostile because of what he has had to deal with through the years, with claims made against evolution and constantly having to defend them, when that should not be the case.
Indeed! Consider this example of a Creationist "argument".
In addition to my discomfort with his extreme anti-religious sentiments, I have some scientific objections to Dawkins’ work. In the chapter dealing with the monotremes, we read that the “molecular evidence” indicates that the common ancestor of the platypuses and the echidnas lived only 20 million years ago, but that fossil platypuses have been found that are older. So Dawkins says, “This would mean that echidnas are modified platypuses who left the water within the last 20 million years, lost the webbing between their toes, narrowed the duckbill to make an anteater’s probing tube, and developed protective spines.”
This idea violates the principle in science of parsimony, that the simplest explanation that involves the fewest assumptions is most likely to be the correct one. I would suggest instead that the method that Dawkins relies upon of dating splits between animal lines may not be as accurate as one would think. When there is a conflict between two lines of evidence, that is proof that one line is prone to be less accurate than the other. And in this case, I would trust the fossil record more and thus reach the conclusion that the split between platypuses and echidnas took place long before 20 million years ago and that their concestor probably looked like neither of them. Just because DNA and protein sequences are prone to change over time does not mean we should rely on them exclusively to date when common ancestors of living species lived and ignore other evidences that indicate a different conclusion.
It must be noted that while rejecting his idea about the recent evolution of the monotremes, I am in no way denying the possibility of analysis of molecular evidence being useful in establishing the relative distances in relationships. I just doubt that it is reliable in all cases in establishing an absolute indication of when various lines of organisms separated from each other. For example, one may conclude from molecular evidence that hippos are more closely related to whales than they are to any other land mammal, relatively speaking. But any suggestion of an exact date of the separation between the ancestors of the hippos and the ancestors of whales would have to wait for confirmation from the fossil record. Thus, while I don’t dispute that platypuses are more closely related to echidnas than to any other mammals, I do not find the idea of a separation of their ancestors only 20 million years ago to be at all realistic. And most of the dates of the “concestors” given in the book may also be questionable, as Dawkins himself admits for some of them in the book itself. It is entirely possible that 20 or 30 years from now, most of The Ancestor’s Tale will have to be remade into a new edition.
I mention this because of notorious habit of creationists of misquoting the writings of evolutionists like Dawkins, Gould, and others to make them look like they said things that in fact they did not. I naturally assume that the same could happen to me here as well.
The most recent common ancestor (MRCA) of any set of organisms is the most recent individual from which all organisms in the group are directly descended. The term is most frequently used of humans. The equivalent term concestor was coined by Richard Dawkins.
The MRCA of a set of individuals can sometimes be determined by referring to an established pedigree. In general, however, it is impossible to identify the specific MRCA of a set of individuals, but an estimate of the time at which the MRCA lived can often be given; such estimates can be given based on DNA test results and established mutation rates, or by reference to a non-genetic genealogical model.
The existence of an MRCA does not imply existence of a population bottleneck or first couple. The MRCA of everyone alive today could have co-existed with a large human population, most of whom either have no living descendants today or else are ancestors of a subset of people alive today. This seemingly paradoxical phenomenon can be easily explained, if the nature of lineage is taken into account.
When tracing human lineage back in time, most people look at parents, grandparents, great-grandparents and so on. The same approach is often taken when tracing descendants via children and grandchildren. This approach is misguided, as the numbers of ancestors and descendants seem to grow exponentially as generations are added to the lineage tree. In just 80 generations, the number of ancestors can exceed a trillion trillion.
This simple calculation does not take into account the fact that every fertilisation is really a fertilisation between distant cousins which include second cousins, fourth cousins, sixteenth cousins and so on. The ancestry tree is not really a tree, but a directed, acyclic graph. One can place all living people at the bottom of the graph and ancestors above their descendants. As each generation of ancestor is added at the top of the graph, one of the many top-level ancestors will become the MRCA from whom it is possible to trace a path of direct descendants all the way down to every living person at the bottom of the graph.
It is incorrect to assume that the MRCA passed all (or indeed any) of his or her genes down to every person alive today. Because of sexual reproduction, at every generation, an ancestor only passes half of his or her genes to the next generation. The percentage of genes inherited from the MRCA becomes smaller and smaller at every successive generation, as genes inherited from contemporaries of MRCA are interchanged via sexual reproduction.
It is also possible to use the term MRCA to describe the common ancestor of two or more different species. This concept is described in Richard Dawkins' book, The Ancestor's Tale, in which he imagines a backwards 'pilgrimage' in time, during which we humans 'meet' all the other species of organism with which we share a common ancestor. Dawkins coined the word, concestor, as an alternative to MRCA.
Following the human evolutionary tree backwards, we first meet the concestor which we share with the species that are our closest relatives, the chimpanzee and bonobo. Dawkins estimates this to have occurred between 5 and 7 million years ago. Another way of looking at this is to say that our (approximately) 250,000-greats-grandparent was a creature from which all humans, chimpanzees and bonobos are directly descended.
Further on in Dawkins' imaginary journey, we meet the concestor we share with the Gorilla, our next nearest relative, then the Orangutan, and so on. The MRCA for all living organisms is also known as the last universal ancestor.
Regarding 3) in your first post, Dale:
3. The monotremes (egg laying mammals) concestor with us lived about 180 million years ago, at the beginning of the Jurassic period. Had the dinosaurs never evolved...
It's interesting that mammals might have had a lot going for them much earlier if not for the events of the Permina extinction. There are a few good populr science bboks about the Permina extinction - Gorgon, by geologist Peter Ward, is also a great read. The dominant large terrestrial animals before the Permian extinction were the mammal-like reptiles, from a few or a single surviving genera of which true mammals evolved. But the climate change of the causitive events of the PE, possibly huge basaltic lava outpourings from what are now known as the Siberian traps, dumped enormous quantities of CO2 and oither gases and particulates into the atmosphere and, possibly be killing most plant life due to acidity or other toxic components, also apparently caused a severe drop in the O2 concentration of the atmosphere, which resulted in atmospheric composition unfavorable to O2 loving mammals. Birds and dinosaurs apparently have and had lng structures better able to utilize O2 at slightley lower levels. However, mammals did evolve and simply had to settle for small critter ecological niches for many millions of years. THERE WAS A FOSSIL FIND A FEW YEARS AGO OF A JURASSIC perhaps fox sized mammal with a baby dino skeleton in it's abdominal cavity. So while the dinos may have ruled, they weren't always respected by a hungry mammal.
I think the fact that dinos held onto all the large terrestrial animal niches wasn't such a good thing for them. Excepting birds, the smallest dinos in the late Cretaceous were about the size of a wild turkey, and dino diversity had declined by the end of the Cretaceous. ( see Dinosaur Heresies) Mass extinctions do seem to be a bit harder on the big guys (there are exceptions) and having lots of little mammals in lots of niches may have made it easier for the mammals to get through the kT extinction. Dominating may mean a different thing in evolution than in politics, just as Darwinian competion doesn't necessarily mean bloody conflict.
If we all had six arms, eight legs and three heads then NOTHING would change.
The earth would still have thousands of religious rulers claiming that only they know what God MEANT to create and fighting wars with their national armies to impose and enforce their magic lies upon their neighbors.
The truth about that faked video:
In September 1997, I allowed an Australian film crew into my house in Oxford without realising that their purpose was creationist propaganda. In the course of a suspiciously amateurish interview, they issued a truculent challenge to me to "give an example of a genetic mutation or an evolutionary process which can be seen to increase the information in the genome." It is the kind of question only a creationist would ask in that way, and it was at this point I tumbled to the fact that I had been duped into granting an interview to creationists - a thing I normally don't do, for good reasons. In my anger I refused to discuss the question further, and told them to stop the camera. However, I eventually withdrew my peremptory termination of the interview as a whole. This was solely because they pleaded with me that they had come all the way from Australia specifically in order to interview me. Even if this was a considerable exaggeration, it seemed, on reflection, ungenerous to tear up the legal release form and throw them out. I therefore relented.
My generosity was rewarded in a fashion that anyone familiar with fundamentalist tactics might have predicted. When I eventually saw the film a year later 1, I found that it had been edited to give the false impression that I was incapable of answering the question about information content 2. In fairness, this may not have been quite as intentionally deceitful as it sounds. You have to understand that these people really believe that their question cannot be answered! Pathetic as it sounds, their entire journey from Australia seems to have been a quest to film an evolutionist failing to answer it.
With hindsight - given that I had been suckered into admitting them into my house in the first place - it might have been wiser simply to answer the question. But I like to be understood whenever I open my mouth - I have a horror of blinding people with science - and this was not a question that could be answered in a soundbite. First you first have to explain the technical meaning of "information". Then the relevance to evolution, too, is complicated - not really difficult but it takes time. Rather than engage now in further recriminations and disputes about exactly what happened at the time of the interview (for, to be fair, I should say that the Australian producer's memory of events seems to differ from mine), I shall try to redress the matter now in constructive fashion by answering the original question, the "Information Challenge", at adequate length - the sort of length you can achieve in a proper article.
(Dale H: Go to the link above to see the rest of the article. Or, for a simpler explanation that I wrote, go here: The possible role of nondisjunction in evolution. )