Friday, December 27, 2013

An update and ...More about evolution in textbook

I am feeling better now and have begun to sit for some time. I will begin my regular posts in a couple of weeks after a brief  trip which I shall post later. In the meantime, I will publish the post that I had almost completed before my back pain. I thought you would like some light reading while relaxing! Happy New Year!

Lawrence Krauss never tires of saying that “The purpose of education is not to validate ignorance, but to overcome it”. In some chapters of various  textbooks, the word 'animals' is used excluding humans thus privileging humans over other species.When David Attenborogh was asked what would be the single piece of information he would like everyone to know, he said that it would be that all organisms on earth are related.  There is no natural category of animals that excludes humans. Humans are animal, mammals, primates, apes. In this talk, Robet Sapolsky tells of the various ways in which human behaviour is like that of other animals and of the various ways in which it is different.

Evolutionary tree

Tree-thinking is essential for understanding evolution. The only diagram in On the Origin of Species is a hypothetical evolutionary tree. If the history of life forms a tree then a common ancestor can be found for any pair of existing species by tracing each twig back through its branches till they intersect at a common node. It is important to note that the branches and nodes represent populations not individuals.There is very brief discussion about evolutionary trees in the textbook which is inadequate. The diagram given in the book is also wrong. It shows trifurcations at the nodes whereas standard evolutionary trees show bifurcations. More than 2 branches at a node indicate areas of uncertainty.

This tree-thinking makes it easy to answer the common creationist argument: “If humans evolved from monkeys, why are there still monkeys?” The answer is that humans did not evolve from monkeys. The correct statement is that humans and monkeys evolved from a common ancestor who was neither a monkey nor a human. No living species evolved from any other living species. (This site tells you when the common ancestor of any pair of organisms lived.) Something like a 'crocoduck' can never evolve. If ever something like a crocoduck is found, it will disprove evolution. As is usually the case,the closed-minded one in this debate calls the other person closed-minded.

Take the specific example of humans and their nearest relatives, chimpanzees. Humans and chimpanzees evolved from a common ancestor who lived about 6 million years ago and was neither a human nor a chimpanzee. Fossil evidence indicates that this common ancestor would have looked more like a chimpanzee than a human. Since this split from the common ancestor both lineages have been evolving independently.

It is only in retrospect that we can see this split. If a paleontologist was present at the the time of the putative split or even a few thousand years later, she would not have seen anything extraordinary. The two incipient species would just have been two slightly different populations of the same chimpanzee-like creatures and she would have been hard put trying to distinguish between the two lineages that would eventually evolve into chimpanzees and humans.

The positive aspect of the textbook is that the chapter on evolution is the first chapter instead of the last. But, for what is the overarching theory in Biology, the coverage is grossly inadequate. The lack of proper evolution education  in schools is reflected in the fact that hardly anyone knows how drug resistant bacteria develop. (It has been cited as an example of the tragedy of the commons.)I get scared by the casualness and negligence in antibiotic use. In The Greatest Show on earth, Richard Dawkins writes:

I was mildly irritated to read a pamphlet in my doctor's waiting room warning of the danger of failing to finish a course of antibiotic pills. Nothing wrong with that warning but it was the reason given that worried me. The pamphlet explained that bacteria are 'clever', they 'learn' to cope with antibiotics. Presumably the authors thought the phenomenon of antibiotic resistance would be easier to grasp if they called it learning rather than natural selection. But to talk of bacteria being clever, and of learning , is downright confusing,and above all it doesn't help the patient to make sense of the instruction to carry on taking the pills until they are finished. Any fool can see that  it is not plausible to describe a bacterium as clever. [I am not so sure. - Suresh] Even if there were clever bacteria, why would stopping prematurely make any difference to the learning prowess of a clever bacterium?But as soon as you start thinking in terms of natural selection, it makes perfect sense.
Like any poison, antibiotics are likely to be dosage dependent. A sufficiently high dose will kill all the bacteria. A sufficiently low dose will kill none. An intermediate dose will kill some but not all. If there is genetic variation among bacteria, such that some are more susceptible to the antibiotic than others, an intermediate dose will be tailor-made to select in favour of genes for resistance. When the doctor tells you to finish taking the pills, it is to increase the chances of killing all the bacteria and avoid leaving behind resistant, or semi-resistant mutants. With hindsight we might say that if we had all been better educated in Darwinian thinking we would have woken up sooner to the dangers of resistant strains being selected.
As Lawrence Krausss says in this discussion with Richard Dawkins, evolution should be used as a hook to attract students to biology. Otherwise biology is just a collection of interesting facts that appear to be random. This article gives some cribs by various animals about what evolution has saddled them with. The recurrent laryngeal nerve of the giraffe is a stark example of bad design. (It is demonstrated in this dissection.) Here are some examples of bad design in humans. This article has a cartoon which states, 'Oh, I know that He works in mysterious ways. If I worked so mysteriously, I will get fired.' All these design faults can be easily explained by evolution. As Theodosius Dobzhansky said, 'Nothing in Biology Makes Sense Except in the Light of Evolution.'

The process and pattern of evolution cannot be understood without studying about Deep Time and plate tectonics. These are discussed in various textbooks but all 3 are never combined in an interesting way. Here is an interesting example covering all 3 ideas. For the two of who are still reading this post (I am an optimist!),here are a few ideas about evolution that should have  been stressed.

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