Dreamer Easy

Continuing today's summary, with nested hierarchies. There is scary maths, but also a fairly simple example of the sort of pattern that common descent ought to cause. Here's my own diagram, based on the para about plants:

This is more than just a tidy classification - it reflects how plants actually evolved. If common descent was wrong, we'd expect to see (for example) non-vascular plants with seeds (or for that matter mammals with feathers). But each group of living things inherits whatever characteristics its ancestor had. (Similarly, you can classify human languages any way you like, but only one "family tree" will correctly show how each language developed from previous ones.) Although hundreds of thousands of species have been discovered, all of them fit into this sort of hierarchy (there are no mammals with feathers!).
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(If you'd like an example of a smug ID critic getting their bottom kicked thanks to their own ignorance, look no further than this thread, in which I first encountered the idea of nested hierarchies as evidence of evolution - though I had grasped the basic idea as a kid, and was so fascinated I went about the house applying binomial nomenclature to the potted plants. Quelle g33k.)

Time to continue summarising the evidence for macroevolution (the appearance of new species, families, phyla, etc) as outlined over here. The author doesn't know I'm doing this - any screwups are my own fault. Comments, questions, etc are very welcome!

Firstly, The fundamental unity of life.

All living things need to reproduce and to use energy, and to catalyse the chemical reactions that do this (a catalyst speeds up the reaction). If common descent is correct, and all living things descend from a single ancestor, then they should have inherited the same chemicals for doing these things.

That's exactly what has been found. All living things use either DNA or RNA to reproduce. They use exactly the same versions of those chemicals, out of a huge number of different possible versions. The same genetic code - the way information is stored in the DNA or RNA - is found in all living things (except for a few small variations). All living things use enzymes, made of proteins, as catalysts. To build those proteins, they use the same set of 22 amino acids, out of hundreds of possible choices. Basic chemical reactions needed for life, such as breaking down glucose to release energy, are done the same way in all living things, using the same enzymes. All living things use the same molecule to store energy, ATP - again, out of hundreds of possible choices.

This allows scientists to predict that when new species are found, they will always have the same genetic code, use ATP, etc. There's no reason they have to use those particular chemicals, out of hundreds of possible choices - except that they all descended from ancestors who used those chemicals.

The next bit of 29+ Evidences for Macroevolution is a daunting introduction to phylogenetics. Luckily, the author says we can have an early mark before the really technical stuff! Anyway, let's see how I go with my crummy summary. (Remember, the essay's author doesn't know I'm doing this. Your comments are welcome!)

If life descends from a common ancestor, then it'll be possible to draw a family tree of every living thing on Earth. Such a family tree is called a phylogeny. There will only be one correct family tree - the true history of evolution. The branches of the tree show how each group of organisms (living things) descended from another group, and the relationship between related organisms, just like an ordinary family tree showing parents, grandparents, cousins, etc.

29+ Evidences gives a phylogeny for all life - you read it from the bottom to the top.

These phylogenies are created by looking at the characteristics groups share with each other - you can see how the tree branches when a new characteristic appears, such as chloroplasts or feathers. The "leaves" on that branch all share those characteristics - humans and cows both have placentas, humans and marsupials both have hair, humans and starfish are both deuterostomes (their embryos develop the same way), humans and jellyfish both have a nervous system. The tree branches and branches again - that's called a nested hierarchy.

A phylogeny can be drawn simply, like a train map, which shows how stations connect but doesn't try to accurately show the distance between them; or like a road map, which does indicate "distances" (for example, how similar a particular gene is). The length of the branches is used to show "distance".

The mathematical methods used to create these phylogenies have been tested against known phylogenies (for example, with strains of mice and of viruses, where their pedigrees were already known); the methods were found to be highly accurate.

A short lay explanation of phylogenies can be found at What Is Cladistics?.

In the next installment - the evidence that all life forms are descended from a common ancestor.

Speaking of evolution, a neat thing I spotted in a recent New Scientist: a newly discovered microbe called Hatena has been seen incorporating an algal cell into its body. It's long been known that eukaryotes (fungi, plants, animals, us) got their start when simple cells took on board other cells as lodgers - algae became the chloroplasts inside plant cells, bacteria became the mitochondria which power our cells. But this is the first time the process has been directly observed.

Hatena is Japanese for (roughly) "What th-!?".

Little Dawkins footnote. The book which he relies on for his knowledge of academic feminism - and how it supposedly rejects science, math, and logic as hopelessly sexist - Professing Feminism - is based on thirty anonymous interviews, which were then generalised to the entire field. The book, just one of numerous successful backlash publications in the nineties, became a handy tool for attacking all women's studies and all feminism based on the disgruntlings of a few.

omg. According to Dawkins, it's possible to induce snakes to grow legs. That is, to switch on the leg genes lying dormant in their DNA.

That's one powerful piece of evidence that snakes descended from a ancestor which had legs - why would a designer, creating the snake as is, include leg genes? (A 95 million year old fossil legged snake has recently turned up.*)

It's also incredibly cool. *goes about making snakes grow legs*


* I don't mean it walked.

I once read a great sentence in National Geographic: "Seeking to learn more about feathered dinosaurs, I flew to China."

Why all the fuss over whether Intelligent Design qualifies as science or not? In the US, where the controversy has come to the boil, religious beliefs can't be taught in the science classroom, at least in public schools, since this would violate the First Amendment, which guarantees separation of church and state. This is why Creationism was presented as "Creation Science" in the eighties, and why it's being presented as "Intelligent Design" now.

(It's also where my earlier question about whether scientists should be allowed in Sunday School is a poor analogy. An invited sceptic is not the same as part of a state curriculum.)

Australia has no Bill of Rights, but the same argument is being presented here.

More links for your reading pleasure!

Science and Creationism: A View from the National Academy of Sciences. Looks like they've put the whole booklet online. Especially see the Conclusion.

The Wedge Strategy makes clear the religious agenda behind ID.

The blog The Panda's Thumb is monitoring the Pennsylvania trial.

Found a ripping 2003 Guardian article on religious scientists. And here's a pointer to the Science and Religion Forum it mentions.

I'm a believer in NOMA - that is, religion in its place, science in its place thank you very much Professor Dawkins. Serious question: if ID proponents are given space in the science classroom to put their views, should "materialist scientists" be given space in the religion classroom (scripture classes, Divinity lectures, Sunday School etc) to put theirs?

New Scientist recently (8 October 2005) ran a series of articles about Fundamentalist* religious belief. The articles were courteous about those beliefs and their adherents (and one piece discussed scientists' tendency to overestimate their omniscience), while still strongly challenging moves from some Fundamentalist quarters to get rid of science. I want to summarise a few key points here.

Three crucial things to know and my suggestions:

- Studies find few differences between Fundamentalists and the rest of us. They are no less sane, smart, sincere, and happy than the average person. Many of them hold comparatively "liberal" political views. Treat them with basic courtesy.

- Fundamentalist theology is not accepted by mainstream religions. Don't equate "religion" or "Christianity" with Fundamentalism or Creationism.

- There is a well-organised, well-funded political Fundamentalist movement, trying to have Intelligent Design taught as science and climate change dismissed as "superstition", with the ultimate goal of replacing science with "faith-based reasoning". Religion should be respected and taught - but not in science classrooms.

( In more detail )

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* A note on terms: some folks prefer to be called evangelical Christians, Bible-believing Christians etc. (There may be Islamic equivalents of which I'm ignorant.) I mean no offence by using the catch-all term "Fundamentalist".