Thursday, August 13, 2009

Not Just A Theory

Evolution



Since I keep getting told there is no concrete evidence for evolution, I'm going to post a short summary of pretty good evidence that is enough to convince me, at least until I see better evidence for another theory.

In my journey through life as I have sought answers, I have come to a road where I no longer feel that I have to contort a particular world view around factual observable evidence, and I am free to interpret the evidence as it is.

Scientists purposefully try and remove as much bias out of their processes as possible so they get the best results in their experiments, and I try and do the same when I examine the results.

That being said, science is a human endeavor and as such is by no means perfect. The catch here is that the scientific process seeks to constantly improve itself and correct past errors. This is a very important concept and is the main reason I trust science more then an unchanging religious text or book. Darwin was wrong about many things in his Origin of Species that we have later updated in the field of genetics and other overlapping scientific disciplines. This does not invalidate the theory of evolution, it only makes evolutionary biology more diverse and interesting as we collect more observable evidence in all the interrelated fields of the life sciences.

I encourage anyone who is reading this to have an open mind to the possibility that their world view might differ from what science has observed, and I will try do to the same when examining the evidence. We should not start out with a fixed idea in our heads about how things should be. As Carl Sagan once said, belief should scale with evidence.

Lets get the basics out of the way -

First, I want to stipulate that the theory of evolution is not the theory of Abiogenesis or the Big Bang. Those are altogether different subjects, regardless of their overlap. Also note that I will not capitalize evolution in every sentence as if it was some kind of religious belief system, which it isn't.

Second, the word "theory" has special meaning in the field of science. I am redefining theory here so that the word's definition is not confused and used in attacking the credibility of the theory of evolution.


http://www.notjustatheory.com/

"In science, a theory is not a guess, not a hunch. It's a well-substantiated, well-supported, well-documented explanation for our observations."

The key word to read in that sentence is "observations".

Thirdly, I am leaving out discussions of morality and ethics since I feel that those subjects will move us into other territory outside of the scope of this essay.

And last, I will not stipulate that there is or is not a supreme supernatural creator or first cause for the universe since my belief is we really don't know, and to claim otherwise puts me back in that position again of contorting my world view around the evidence or vice versa, an unnecessary bias for this essay.

Definition Of Evolution



"In biology, evolution is change in the genetic material of a population of organisms from one generation to the next. Though changes produced in any one generation are small, differences accumulate with each generation and can, over time, cause substantial changes in the population, a process that can culminate in the emergence of new species. Indeed, the similarities amongst species suggest that all known species are descended from a common ancestor (or ancestral gene pool) through this process of gradual divergence" - Wikipedia



We can describe evolution with the following three concepts:

Natural Selection - the process by which heritable traits that make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generations.

Random Mutation - In biology, mutations are changes to the nucleotide sequence of the genetic material of an organism. Mutations can be caused by copying errors in the genetic material during cell division, by exposure to ultraviolet or ionizing radiation, chemical mutagens, or viruses, or can be induced by the organism itself, by cellular processes such as hypermutation.

Genetic Drift - Genetic drift or allelic drift is the change in the relative frequency with which a gene variant (allele) occurs in a population due to random sampling and chance: the alleles in offspring are a random sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces.

The two kinds of evolution we hear about most in conversation are micro and macro.

Micro evolution is evolution occurring over a small period of time, like several generations. We see micro evolution in action when we study the influenza virus.

Macro is the same as micro evolution but it occurs over a much longer period of time like hundreds of thousands or even millions of years. One of the main points of contention with the theory of evolution is that we cannot observe macro evolution, or that it is impossible for macro evolution to have happened since the Earth is not old enough.

The Age Of The Earth



Lets face it, the biggest argument against the theory of evolution is that the Earth is not ~4.5 billion years old but 6-10 thousand years old instead. In my opinion, arguing that the Earth is only a few thousand years old is the same as saying it is flat, since we have more then enough observable evidence that it is much older, but in order to accept macro evolution we must first address this pseudo belief.

What do we have as observable evidence for the ~4.5 billion year old Earth ?

Radiometric Dating



We have many types of radiometric dating, each of which gets calibrated from real world data. Critics will claim that radiometric data gives us unreliable results. This is important to note since almost all physical evidence we have for evolution requires that our radiometric dating system is accurate and does work. Also important to note is that nobody has yet proven that radiometric dating is inaccurate and should be thrown out using the scientific process.

Independent measurements, using different and independent radiometric techniques, give consistent results (Dalrymple 2000; Lindsay 1999; Meert 2000). Such results cannot be explained either by chance or by a systematic error in decay rate assumptions.

Radiometric dates are consistent with several non radiometric dating methods. For example:


  • The Hawaiian archipelago was formed by the Pacific ocean plate moving over a hot spot at a slow but observable rate. Radiometric dates of the islands are consistent with the order and rate of their being positioned over the hot spot (Rubin 2001).


  • Radiometric dating is consistent with Milankovitch cycles, which depend only on astronomical factors such as precession of the earth's tilt and orbital eccentricity (Hilgen et al. 1997).

  • Radiometric dating is consistent with the luminescence dating method (Thompson n.d.; Thorne et al. 1999).

  • Radiometric dating gives results consistent with relative dating methods such as "deeper is older" (Lindsay 2000).


Saying that radiometric dating does not work is a straw man argument. If Young Earth Creationists could prove that it is not accurate, they would publish a peer reviewed scientific study on it and get a Nobel Prize, which they have not. The entire scientific community regularly uses radiometric dating in almost every field, and where the fields overlap the data has been consistent and verifiable.


Geochronology


Evidence from radiometric dating indicates that the Earth is about 4.570 billion years old. The geological or deep time of Earth's past has been organized into various units according to events which took place in each period. Different spans of time on the time scale are usually delimited by major geological or paleontological events, such as mass extinctions, which has created many fossils for us to find and study.

Scientists are able to find fossils in different layers of the geological column that match up with our understanding of evolution. For example, we do not find fossils of dinosaurs at the same place in the geological layer as human fossils because they existed at different time periods in the Earth's history.

Scientists have also been able to follow the evolutionary progression of organisms from layer to layer using transitional fossils.

Critics are quick to point out that we don't have all the transitional fossils (which is impossible), but we do have many, and as we continue to find more they only strengthen the observable evidence for evolution rather then weaken it.

Some links of interest:

http://en.wikipedia.org/wiki/List_of_human_evolution_fossils
http://darwiniana.org/hominid.htm

Transitional Fossils


In the previous section I linked to some sites with a catalog of transitional fossils. Critics of evolution will very often make the claim that we do not have transitional fossils. We do ! You can Google indexes of thousands of them. Not only that, but we have a testable hypothesis for verifying if they are transitional or not. Here is a video that explains one way we do this:

Video pt 1
Video pt 2

The Moon



Humans have walked on the moon. If you think this is a conspiracy and not true, don't bother reading this section because I'm going to assume for the purposes of this essay that it really happened.

While we were there, we gathered many geological samples (rocks). Why do we want rocks from the moon ? To study of course !

One of the first things done on the rocks was to date them using radiometric dating. We discovered from these tests that the moon is about the same age as the Earth, confirming and further elaborating on the results we have from testing the age of rocks on Earth.

Some critics say that the rate at which the moon recedes from orbit around the Earth is proof that the Earth is only several thousand years old. To this argument I refer to this very lengthy essay on the subject : http://www.talkorigins.org/faqs/moonrec.html

The short answer to that criticism is that the orbits of the planets and moons in this solar system are not static but continually change over time and push and pull on each other, sometimes to states of temporary equilibrium.

Genetics



In the field of genetics, scientists who have sequenced the human genome can see a hierarchy of the tree of life in the code of our DNA. This evidence is so well founded that scientists have been able to find things like endogenous retro viruses and other encoded information in human DNA that we share with other living things on this planet, including plants. Humans are just another branch on this gigantic and amazing tree of life.

http://tolweb.org/tree/

Endogenous Retro Viruses


"Endogenous retroviruses (ERVs) are retroviruses derived from ancient viral infections of germ cells in humans, mammals and other vertebrates; as such their proviruses are passed on to the next generation and now remain in the genome. Retroviruses are viruses that reverse-transcribe their RNA into DNA for integration into the host's genome." - Wikipedia

After an ERV infects a host, the host DNA will contain a remnant of the ERV DNA. When this was discovered, scientists compared our human DNA with that of another "great ape" species, the orangutan. What they found is startling; we have the same ERV encoded information in the same places as they do in our DNA ! Not just in one place, but many.

The scientists who discovered this came to the conclusion that orangutans and humans share a common evolutionary ancestor. This was already a theory, but this genetic evidence confirmed it.

Random change you say ? How about a little probability game then :

http://www.youtube.com/watch?v=TUxLR9hdorI

A New Species



A common argument against the theory of evolution (or rather, macro evolution) is that we have never observed a new species being created.

This is a tough one since the scientific community itself has a hard time agreeing on just what is a new species, or how to define "species".

One definition is:

"... that stage of evolutionary progress at which the once actually or potentially interbreeding array of forms becomes segregated into two or more separate arrays which are physiologically incapable of interbreeding." (Dobzhansky 1937)

For a verbose listing of examples of instances of speciation, please read this publication:

http://www.talkorigins.org/faqs/faq-speciation.html

There have been many cases of fruit flies, plants, beetles, etc.

Conclusion



In conclusion I think that science is our best bet for understanding the mechanics of our universe within the limits of human imperfection, and the theory of evolution best fits with the current observable evidence.

Religion had its chance to explain things and often got it wrong. Why should religion continue to be allowed this position in our society ? Religion should be for our better understanding of our spirituality or divinity (or lack thereof), not a final authority on the idea that the world is flat or round.

To the critics of evolution- if your side of the debate is founded on real science then you have a way to get your message heard and it is through the exercise of the scientific process.

For the purposes of any discussion after I post this essay, I do not accept articles from Answers In Genesis or other religiously biased institutions to be good rebuttals to peer reviewed scientific studies. If you wish to be persuasive when debating with me against evolution please use peer reviewed scientific studies or publications.

References:
Posted by at No comments:
Subscribe to: Posts (Atom)