Evolution Explain, Part 4 – Science and Prediction

TRiktaalik

Science With My Doctor

I was in an accident once and was prescribed three kinds of medication. I told my doctor I would like to drop one I was taking twice a day. It was given as a prophylactic, and I was unsure if it was doing anything. I’ve never been on medication before and my doctor shares my feeling that no meds are good meds.

So she set out a plan: You’re taking two pills twice a day. Start by dropping one of the morning pill. Try it for a week and see how you feel. If you don’t notice any effect, drop another one from the afternoon. Keep doing this until you aren’t taking any. If you get to where you are feeling symptoms, you’ll know that you’ve found your threshold.

The Scientific Method

It was a good plan and seemed to be a perfect application of the scientific method.
There is nothing sacred about the scientific method, and it’s not codified into any kind of scripture. Depending on where you look, you’ll find anywhere from five to eight steps. It is simply a way of looking at a problem and working it out. Though there is no agreed upon definition, all will incorporate the following:

An observation is made.
A question is asked based on the observation.
A hypothesis for the question’s answer is made.
The hypothesis is tested and determined to be true or false.
A conclusion is derived based on the tests and the evidence.

As an example, let’s say you find a rock. It’s goldish and your pals think you’ve struck Montezuma’s gold and spend their time figuring out how to spend your money. Great, except for one thing: Dad is a geologist and says you’ve found a nice hunk of Fool’s Gold. How to tell the difference?

You you have a problem: is this hunk of something really gold? You hypothesize that it is. To test your hypotheses, you compare your chunk to the known characteristics of gold. You won’t know if you have pyrite or not and comparing your chunk to the characteristics of gold might not even tell you if you have gold, but it will tell you if you don’t have gold. Science is tricky.

You pull up Wikipedia and read that gold is a ductile metal and is usually found as a nugget or grain. What you are holding is a solid mineral that looks like dice stacked together. You read that gold scratches easily. You grab Mom’s nail file to scratch your rock and can’t make a mark. Finally, you read about streaking or rubbing the rock to get a color. You find an old tile from when your parents re-did the shower and scratch your stone across the back. You read that gold leaves a line that is goldish-yellow. Yours, though, leaves a greenish-black line of dust. You hand it back to your friends. Not gold. You don’t know what it is, but in science, knowing what something isn’t is just as important.

This is similar to when your mom decided that your little sister is lactose-intolerant. She noticed that every time your sister has ice-cream for dessert; she ends up with a stomach ache. Your Mom makes an observation and asked a question: is the girl lactose-intolerant? She has her daughter abstain from her ice-cream habit for two weeks. She does and has no stomach ache. This isn’t proof that she is lactose-intolerant: there are a dozen reasons she might be sick from eating ice cream. But she’s found a correlation, and that important, too.

Is evolution falsifiable?

It is. The evolutionist J. B. S. Haldane was famously asked the same question and responded that “rabbits in the Precambrian” would disprove evolution. What he meant was that any gross error in the geologic column would show that descent as we understand it hadn’t occurred. Richard Dawkins agrees and argues that fossil mammals in the Precambrian would “completely blow evolution out of the water.” The philosopher Karl Popper referred once to evolution as unfalsifiable. Anti-evolutionist still bring this up as scripture. Popper later complained that he was misinterpreted, arguing that evolution is difficult to disprove when compared to sciences like chemistry or physics. The falsehood of the statement “pouring salt into water turns water to a blue color” is easily tested: pour salt into water and watch for the color change. That animals are genetically related is more difficult to assess, especially with the time scale involved

One of the most exciting finds in recent years using the scientific method was the story of Tiktaalik that Neil Shubin outlines in his book Your Inner Fish. In the opening chapters, he talks about making plans to find what they are hoping to find: an evolutionary intermediate between something living in the water and something that lives on land. He knows the task is daunting: 99% of earth’s species are extinct and fossilization is rare. To maximize the effort, he looks for three things:

Rocks of the right age.
Rocks of the type to preserve fossils.
Rocks that are exposed at the surface.

Shubin and his team start filling in the blanks. He knows that all early animal life occurred in water. We have tons of evidence of fish but no land animals to around 385 million years ago. Around 365 million years ago, we find fossil evidence of amphibians and reptiles. So Shubin needs rock around 375 million years old to find this intermediate. With this information, he begins thinking about rock. We know that igneous (volcanic) and metamorphic rocks aren’t conducive to fossilization. Volcanism melts everything and metamorphosis squeezes and squishes and breaks everything. The great bulk of fossils are found in sedimentary rocks that are laid down over time by silt in oceans and river beds. Now Shubin knows two things: he is looking for sedimentary rock formations about 375 million years old.

Is there anywhere these rocks exist exposed for exploration? In an exciting part of Shubin’s tale, they stumbled unexpectedly upon a map showing exactly what they were looking for. The map was of North America to the Arctic and delineated three distinct areas where sedimentary rocks of this age (Devonian) are located. One was in Greenland, one in Pennsylvania, which Shubin had been exploring for years, and one was in the upper reaches of the Arctic. For reasons outlined in the book, the group chose the Arctic to search for their land-grabbing fish. They analyzed, studied and gathered information, then made their prediction: if this thing can be found, then this is one of the places we should find it.

Tiktaalik

You can guess how the story ends. It took several years and several trips, but one day, as everyone was settling in for dinner, one of the team members ran into the tent ‘wild-eyed’ and ‘out of breath’. He had found, on the side of a nearby hill, a ‘carpet of fossil fish bones’. Over the next several days they scoured the site until they found what they were looking for – a broad, flat skull jutting out from the rock face – hopefully with an intact skeleton encased within the rock. Shubin comments that “What we saw gradually emerge from these rocks during the fall of 2004 was a beautiful intermediate between fish and land animals.” They asked local natives to name the animal and two names were suggested: Tiktaalik – named for large freshwater fish’ was chosen because it was the only name the team could pronounce. Thus, we have maybe the most celebrated intermediate known to date. More will be found, maybe even by Shubin, and all will follow the same pattern using this method of using existing and observable knowledge to predict what we should find and where we should find it.

To summarize Shubin’s work with Tiktaalik:

    We want to find a fossil representing the shift from sea animals to land animals
    We need to find an area with rocks that support fossils, are of the right age, and are exposed.
    Rock must be about 375 million years old.
    Rock must be sedimentary.
    Rock must have exposed faces.
    The Upper Arctic is chosen as a likely contender.

    Tiktaalik is found exactly where the science says it should be.

Shubin on Wiki.
Shubin at the University of Chicago.

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It’s a great read.

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