The Fossil record: The first few eras

Fossil Record 1The Precambrian Era

This era consists of seven eights of the earth’s history. Its fossil record consists of very simple organisms, most organisms with no nuclei (prokaryotes) – like bacteria. Eventually, organisms with nuclei (eukaryotes) appear. Multi-celled organism appear towards the end of the period but they are not rabbits or any thing of the sort. They are all still microscopic.

The Cambrian Era

This period begins with the sudden appearance of complex life forms – sudden in that there is nothing from the previous period would lead you to expect them. From the simple microscopic single celled organisms we had at the end of the Precambrian era, we have the fossils of almost all the major phyla in the animal kingdom. This is called the Cambrian Explosion.

A phylum (plural phyla) as pertains to this discussion is a ‘body plan’. An example is the arthropods whose body plan includes an external skeleton, a segmented body, and jointed appendages. Examples of animals in this class are spiders, scorpions and centipedes.

A popular explanation for Cambrian explosion is that the fossilization of hard bodied animals is more likely and so the soft-bodied precursors to the Cambrian fossils were not preserved. Of course, there are quite a few soft bodied fossils from both the Precambrian and the Cambrian eras, so this argument is not wholly adequate.

The Cambrian era ended with a mass extinction.

The Ordovician Era

This era was dominated by invertebrates – animals without backbones. Many types of snails and clams are found for the first time in this era. While the organisms were new, the body plans had already been set back in the Cambrian era. Some vertebrates are also found in this era.

The Silurian Period

Like the Ordovician, life in this period was mostly marine. There were new animals found, but once again with no new body plans.

Sources:

http://www.ucmp.berkeley.edu/help/timeform.php

http://www.fossilmuseum.net/

http://science.nationalgeographic.com/science/prehistoric-world/cambrian/

http://science.nationalgeographic.com/science/prehistoric-world/precambrian/

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A word of caution: Pictorial representations of the fossil record suffer from one problem: they can be manipulated to show what the author wishes to show. If I picked only the microscopic organisms from each period, I can produce a pictorial representation that is mostly unchanged to suggest that evolution did not occur. If I pick organisms with gradually increasing size, I can give the impression of organisms getting more complex with each period – although this says nothing about complexity, but size. I will work on providing an accurate (as far as I know) pictorial representation of the geologic time periods, but it will be slow work.
I also want to emphasize that evolution is not about new types of organisms appearing – they do so all the time in the geologic record. It’s about the progression. If every time period had new organisms but all the organisms had no significant new features, this would be uninteresting. 
If, on the other hand, new organisms appeared and each successive organism was less complex that its predecessors, that would hardly support Darwin’s theory. 
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The Evidence for Evolution: The Fossil Record

This one is supposed to be from a crocodile

I went to an archeological dig yesterday. It was tiring, but helpful. I’ve been having trouble with my research because people tend to feed me bits of information rather than the raw data I want – I find anything but raw data hard to swallow. As a result of that trip, I was finally able to wrap my head around one issue in this debate: the fossil record as evidence for Evolutionfootprints unbroken.

The case of the Footprints

Note: This example assumes that we do not get into the size of the footprint. Many people have the same size foot anyway.

To see this, picture yourself walking on a sandy beach. You’ll leave a trail of footprints behind you for as long as you walk. Someone else coming upon this trail will find themselves thinking that a human being must have walked from point A to point B leaving that trail.

Notice that this uses inductive reasoning. The person knows (1) That human beings can leave such a trail and (2) That human beings often leave trails like that. As a result, the explanation is possible and plausible. The person then concludes that this is the best explanation. It is possible that this explanation is wrong – possible, but not likely. Unlike deductive reasoning, one can’t be absolutely certain, but they can be pretty darn sure.

footprints partially brokenNow, imagine that there are more people on the beach. They throw balls, set up umbrellas and picnic cloths and play all sorts of games. In the process, they destroy some of your footprints – just a few here and there. Looking at the footprints, you can still be pretty sure that they were made by one person walking from point A to B. But as more footprints are destroyed, your certainty should decrease. What should make you think  that a footprint here and there were made by one person walking from one place to another?

footprints completely brokenImagine then that a big wave comes and washes away all but the very 1st and last footprints. Imagine also, that these footprints were 30 feet apart. If you told someone that the footprints were made by one person out for a walk as the person walked from point A to B, why should the person believe you? They should respond with incredulity. It’s possible, but given the vast number of people who come to that beach, how plausible is it? And even if it were plausible, what evidence do you have for its truth?

 

In this post, I’m going to argue two points.

1. That the existence of an a pretty continuous fossil record, like an almost complete set of footprints, is good evidence for Evolution.

2. That the less continuous such a record is, the less reliable it is as evidence.

Beyond Reasonable Doubt

There are those who do not regard the fossil record as evidence for evolution. As they say, cars today look like but are more complex than cars in previous years, but they didn’t evolve. They were designed. Someone had an idea and numerous people have built on that idea over the years.

Those who say so have a good point. The existence for similarities between things that existed in successive time period does not necessarily imply evolution in the biological sense (the neo-darwinian theory of mutation and natural selection). But it does suggest evolution. It is simply  the mechanism of the evolution that changes. The mechanism in this case is intelligent beings. Some people built the first car and humans kept adding a little to it, one at a time, till we got where we are today. Every new car after the first used some of the ideas already actualized. They did not start from scratch.

A set of footprints on a beach and the knowledge of a path* by which they could be formed by one individual do not constitute evidence beyond all doubt that the footprints were made by one person. But they do constitute evidence beyond reasonable doubt.  A set of cars showing the change in cars from their first creation till now, and the knowledge that humans can use previous ideas to evolve the idea of a car (i.e. create cars that are similar to older models, but still different) do not constitute evidence beyond all doubt that the cars were made in such an evolutionary manner. But they do constitute evidence compelling evidence in the absence of good evidence to the contrary. Likewise, a progression in time from less complex to more complex living things and a mechanism by which changes can be made to species to transform them into other species does constitute evidence for evolution in the absence of evidence to the contrary.

Notice that I have laid out two basic requirements (there might be more):

1. The presence of a pretty good progression from less complex to more complex.

2. The presence of a mechanism by which the evolution can be carried out.

Mugs sort of look like plastic cups, but they can’t evolve from each other. So no matter how much alike they might look, they didn’t evolve. They were made for similar purposes and that purpose has certain requirements (to be solid, waterproof and have a hollow, for example). That’s why they look alike. On the other hand, airplanes could have evolved from bicycles. The mechanism (humans with creative ability) is present. But there’s no progression that we (well, I) know of.

How Continuous should the record be?

Think back to my footprint illustration. The reason we know someone walked from point A to B is that we can see a good progression. However, in the last photograph, we can’t make that conclusion. We just don’t have enough evidence so making such an argument would require great imagination. The progression is only good evidence as much as it is a progression. Two footprints 30 feet apart is not a progression. Two adult footprints 30 feet apart and a few child’s footprints in between is also not a progression. That’s why people talk about the ‘gaps’ and ‘inconsistencies’ in the fossil record and talk about how ‘complete’ the fossil record is. There is no magic number at which a gap becomes too large. What some people find convincing, others won’t. We’ll never get a complete fossil record, so the question is: how good does it have to be in order to make Evolution beyond reasonable doubt? That’s like the question: how wide a pit is too wide to jump across? 30 feet is too wide for everyone and 2 inches is really small. But somewhere in the middle, the answer isn’t the same for everyone.

Still, when I am told that the fossil record is ‘overwhelming evidence’ for Evolution, I can’t help but think that these people mean that the fossil record is almost complete. I haven’t seen the fossil record, but can that many Frenchmen be wrong? I’ll let Alex Rosenberg tell me.

What would disprove Evolution?

Besides the second coming? I haven’t thought about that very much. There is room for attack on it, however. A very bad fossil record and the absence of a path* should force one to relegate it to the status of a hypothesis, but as for disproving it, we can’t make an argument from silence.  We’ll need evidence that it is false.

*I explain what I mean by a path in Why Evolution Needs Mutations

Now, as if you needed pictures:

They said it was a dinosaur bone. It sure felt like a rock to me.
They said it was a dinosaur bone. It sure felt like a rock to me.
This one is supposed to be from a crocodile

archeological dig

Why Evolution Needs Mutations

I stopped by the Freethinkers table at my school’s activity fair recently. They had a number of tracts on their table. When I spotted one on Evolution, I picked it up. I’ve been writing about evolution for a while and tracts are quick to read. The title: “Evolution in a Nutshell”.

It was a quick read. It was mostly a theoretical explanation of the theory of evolution. It first explained artificial selection, then explained Natural selection and Niches – all things that should be reasonable simple and uncontroversial (at least at the basic level). Then, it proceeded to contrast micro and macro evolution.

Some critics of evolution assert that this only describes “micro-evolution”. They say that “macro-evolution”, where creatures change to form a new “kind” has never been observed. This is like saying that 1 + 1 may equal 2, but no one has ever counted to a million, so it is impossible to get to a million by starting at 1. Or, I can walk to the corner store, but it is impossible to walk across the country.

The answer is the same in each case is the same. Yes you can. All you need is enough time.

ladderThe Case of the ladders

Look at ladder A on the right of the page. Can you climb to the top of the first ladder? Of course. You can climb to the first rung, from the first rung, you can climb to the second, and then to the third and so on. Can you climb to the top of ladder B? Not unless you have extremely long legs. You can climb to the fourth rung, but that’s as far as you get. What then would you say to the writer of the above paragraph when he says

That’s like saying 1 + 1 = 2, but you can’t count from 1 to a million. Yes, you can. All you need is enough time.

Obviously, that person is missing one crucial fact. You don’t need just time to get to a million, you need a path. The reason you can get from 1 to a million is that from any point, you can always add 1 and get to the next number. The reason you can climb to the top of ladder A is that from any one rung, you can always get to the next rung. The reason you can’t climb to the top of ladder B is that there is no path to the top that you can take.

Why am I picking on this one inaccuracy? Because natural selection is the only evidence presented for Evolution in the text. Furthermore, the text asserts that Evolution isn’t blind chance, or random because natural selection isn’t random. They practically argue against the idea that mutations are necessary in the Darwinian theory of evolution. So, their case stands or falls on the efficacy of natural selection. In the tradition of encouraging knowledge and fighting ignorance, I felt obliged to point out their error. OK, you got me. I hate missing a chance to tell someone how wrong they are.

Why are Mutations Necessary?

Point 1: Natural selection, as the term implies, works by selecting from things that are already present. For instance, if you have a basket of fruit, you can select from them based on color, type of fruit, weight, etc. But if there is nothing in the basket, or all the fruits have the same characteristics, selection (natural or artificial) is useless.

Point 2: natural selection works by eliminating characteristics from the pool. Imagine a basket containing red apples, green apples, carrots, bananas, oranges and grapes. Let these be my species. Now, I am the representing the forces of nature, selecting members of a species (fruit from the basket). Any fruit that I like, I eat. Those I hate remain.

Stage 1: I like fruits that aren’t roughly spherical. So, I’m going to eat them out of the basket. This gets rid of the carrots and bananas.

Stage 2: I like fruits that are cool in color, so I eat the grapes and green apples.

Stage 3: I like fruits that are not red, so I eat all the fruits except the red apples.

At this point, I have little to select. I can select the apples based on weight and such, but due to the homogeneous nature of my fruits, I’m not going to get any basket different from what I have. This is what is called a limit to natural selection. It is like the fourth rung on ladder B in the example above. There is no where to go from there.

643px-Explanation of Evolution v2.1
643px-Explanation of Evolution v2.1 (Photo credit: Wikipedia)

Point 3: Natural selection produces a mostly homogeneous collection of a species.  See point 2. Also note the increasing uniformity in the picture on the right.

Point 4: Natural selection often makes species less likely to survive when their environment changes. How do I know this? Imagine my sister shows us and she likes only sugary fruits. Having lost the variety of fruits in my basket, how many of them would she eat? A lot. Imagine my brother then shows up and he loves apples. I now have a total of zero fruits in my basket. Note that if the forces of natural selection (aka me) had not done the selection, my sister would have eaten everything except the green apples, carrots, and bananas. My brother would have eaten only the green apples, and my species wouldn’t be extinct.

The larger the variety in the species, the more resilient it is. The more natural selection that occurs, the less resilient it is.

In conclusion

Natural selection does not create diversity. It depends on diversity being already present. It does not preserve or increase this diversity; it reduces it. It does not make a species more likely to survive. The loss in diversity it produces reduces the viability of the species. So, how exactly does such a process create a progression of species from less complex to more complex and from less diversity to more diversity as the Darwinian theory of evolution requires?

It doesn’t. Mutation does. Mutation is what changes the genetic structure of a species. Mutation can create diversity. Mutation can lead to a more complex species arising from a less complex one. But (and here’s the rub), mutations are the thing that make evolution very improbable and reliant on chance. Don’t take it from me. Take it from this online pro-evolution textbook.

The Secular Student Alliance should not have published that tract.

Evolution in Theory

Discovering the means of mutation
Discovering the means of mutation (Photo credit: Noah Sussman)

I know someone who is a deist, but looks on the Darwinian theory of evolution with disdain. To put it mildly, he doesn’t believe in evolution. He frequently posts article on the facebook page that he believes undermine the theory even if those articles are written by people who accept evolution and do not posit that their findings contradict the theory. For instance: Widespread horizontal transfer of retrotransposons and Bacteria May Readily Swap Beneficial Genes: Microbes Trade Genetic Coding for Antibiotic Resistance and More. I say that to say this: in my previous post on evolution, I criticized its supporters’ chronic lack of civility, from insisting that those who reject evolution do so because of their religion to calling them stupid, ignorant, and wicked. I’m newly short tempered so anyone who issues such responses on this post is in for a surprise (no, you will not be banned).

Evolution in Theory

One can explore the theory of evolution in two ways. Firstly, by thinking about it and evaluating its plausibility and possibility and secondly by exploring the physical evidence to see if it really did happen. This is an important distinction because it is perfectly possible for a theory to be both plausible and possible, but not be the case. By way of illustration, it is possible that I cheated on my JSCE. It is also plausible because I, being human, often do wrong things. But it did not happen. On the other hand, if an idea is possible but not plausible, one can rationally reject it in the absence of very strong evidence in its favor.

Is Evolution Possible?

Diagram of mutation and selection in evolution.
Diagram of mutation and selection in evolution. (Photo credit: Wikipedia)

The theory of evolution goes something like this: Organisms adapt to their environment. Organisms of the say type often vary in specific ways. If one of those organisms is different from others in a manner that benefits it, it is more likely than its peers to survive to maturity and pass on its genes. This creates a slow shift in which said characteristic becomes dominant in that species. If this goes on long enough, you eventually get a type of animal very different from the original. This process of change as a result of natural selection is referred to as evolution. Note that in order for this to work, those traits being selected must be genetic or they could not be passed to offspring.

Of course, natural selection won’t work on its own because you need the group of organism to possess genetic characteristics different from each other. Or there will be nothing to select. Think of the very first living cell. It produced offspring and passed its characteristics to them. How then did those offspring become different from each other? That would only happen if the organism failed to pass on its genes faithfully to its offspring.

So the theory of evolution can be summarized thus: Genes can be mutated, creating diversity in the offspring of a particular organism. Those organisms are then selected by their environment because those best able to reproduce do better than the rest. If this process goes on long enough, we get a huge array of living organisms.

I have told a story that sounds possible. It could happen. So did it?

Is Evolution Plausible?

PhotonQ-Homer' s Evolution Theory
PhotonQ-Homer’ s Evolution Theory (Photo credit: PhOtOnQuAnTiQuE)

The whole bulk of evolution hinges on the issue of mutation. Without that, there would be nothing to select. If the first species was terribly unsuited for its environment, it would simply die out. Even already existing species could not change into new ones. Each species would have to be built from scratch. I don’t know anyone who thinks that humans could be built from scratch with no guiding intelligence. We haven’t even been able to build a single cell with guiding intelligence. So, even if that was possible, it would take a damned long time for the diversity we see to  appear; probably longer than the earth has existed.

So, is it plausible that millions of mutations produced the diversity of life on earth? Let’s first get something out of the way: mutations happen. That said,

1. Most mutations are harmful: To make that obvious, consider this example from the University of Utah’s genetics program

Thesunwashotbuttheoldmandidnotgethishat.

Dividing the string into three letter words produces a sensible sentence: “The sun was hot but the old man did not get his hat.” You can try to mutate the sentence, but you’re more likely to get a nonsense statement than a sensible one. For instance, let’s pick a letter to mutate. The ‘b’ in ‘bat’. If we mutated the ‘b’ to ‘h’, we would get ‘hat’ and the sentence would still make sense (somewhat. It wouldn’t get a good grade). However, most of the letters of the alphabet won’t have the same effect. If you picked a letter of the alphabet at random, you would most likely get something like an ‘e’ or a ‘g’, which when substituted for the ‘b’ in ‘bat’, completely ruins the sentence. So going on blind chance only, it is pretty darn unlikely that a mutation would produce a good result.

This ‘bad luck’ can be worked around. As this source makes clear, if the organism accidentally gets two copies of the same gene, one copy can be mutated while the other remains the same. That way, as long as the mutated gene doesn’t dominate the other, work can be done on the other one without killing the organism. Remember that these mutations are all happening by pure chance. Don’t imagine that there are some intelligent choices are being made.

The one issue I instantly see with this is that the mutated gene cannot be selected if it is not in effect. However, if it is in effect, this particular benefit arising from the duplication would be of no use. So, this requires that all modifications of the gene be mutations and that those successive mutations eventually produce something useful. Then that gene has to become dominant.

Here’s the math*:

P1 = Probability that a gene is duplicated X Probability that one of the genes is mutated beneficially X probability that the mutated gene is not dominant (at all stages of its mutation) X Probability that if and when the gene eventually comes online, the changes it has are beneficial.

You can probably tell that I’m not very optimistic about the chances.

2. It gets worse. After all the trouble necessary to create a working mutation, most mutations affect only a single protein product; a tiny change. So in order to create an organism with phenotypic (visible) differences from its parent, you need a lot of mutations. You need the group of genes responsible for that characteristic to be mutated in specific beneficial ways such that they are still compatible with each other. The previously mentioned article argues that this problem can be made easier. Often, some of the genes in that group have a bigger effect than others. So, the more of the more important genes mutated, the more significant the changes in the phenotype. It’s not a breakthrough but it moves the necessary events from really really really unlikely to about really really unlikely.

The math:

P2 = Probability that all the genes responsible for said trait are mutated (or not) in beneficial and compatible manners.

So, the composite probability that a minuscule change in the characteristics of a species occurs = P1 X  P2. Fat chance, huh? And we haven’t even specified that the change in phenotype be beneficial (note that this is different from the change in the genes being beneficial), nor have we gotten into the details of natural selection.

In Conclusion

I’m a huge believer in chance. If a mail arrives in my box with the name of a high school classmate on it and she doesn’t even know my  address, I’ll chalk it up to chance. However, If I arrive home to find a beautiful intricate house of cards on my dining table, you’d better believe I’d be looking to see who broke in. It’s possible that the cards just fell of a shelf and happened to make that house, but I’ll probably never believe that.

This does not mean that evolution didn’t occur – even a little bit. But it does predispose me to the belief that it is not the sole explanation for the diversity of life on earth. It’s possible, but not plausible. My next post on this topic will explore the question of whether there is evidence for the theory.

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* My probability might be rusty. If I made any huge mistakes, please point them out. The calculations are only supposed to be approximate.

My Problem with Evolution

PhotonQ-Homer' s Evolution Theory
PhotonQ-Homer’ s Evolution Theory (Photo credit: PhOtOnQuAnTiQuE)

“To put it bluntly but fairly, anyone today who doubts that the variety of life on this planet was produced by a process of evolution is simply ignorant—inexcusably ignorant, in a world where three out of four people have learned to read and write.”
Daniel C. Dennett, Darwin’s Dangerous Idea: Evolution and the Meanings of Life

It is absolutely safe to say that if you meet somebody who claims not to believe in evolution, that person is ignorant, stupid or insane (or wicked, but I’d rather not consider that).    “Put Your Money on Evolution”  The New York Times  (April 9, 1989)  section VII  p.35

It feels like we learned everything in secondary school – from music, science, to foreign languages*. I took 15 subjects for the first three years, seventeen subjects in the fourth year and nine subjects for the last two years. I wrote three final exams (IGCSE, WASSCE and UME) and then I took the SAT and TOEFL. It wasn’t hard – I didn’t do anything but go to school.

Nigeria’s science curriculum is pretty rough. Between the three standardized exams, we covered everything from the definition of science to Heisenberg’s uncertainty principle. In chemistry we covered everything up till organic chemistry. Biology was the subject in which we had the least work but it was still pretty intense. “Draw and completely label the malpighian tubules of a cockroach” was a question on my final. So I can say I have a pretty solid background in science. I had it beaten into me (figuratively)

And then there’s evolution. I can’t remember if we covered it or not. I know we did punnet squares and Mendel’s laws of inheritance two or three times (in Integrated Science, Biology and Agricultural Science) but I have no recollection of studying Darwin’s theory of evolution. I did, however, have a basic knowledge of the theory. I knew who Darwin was and I was familiar with the most popular evidence for it. If it was in my textbook, I read it. My understanding of evolution up till I left high school went something like this:

Once upon a time there was a tiny single cell which made little baby single cells. Eventually, some of the newborn single cells joined together to form a multicellular organism.  This multicellular organism then made babies of itself and eventually turned into a more complex organism and then organisms just kept slowly becoming more complex until us. Richard Dawkins has an illustration here: http://randalrauser.com/2012/07/the-interrelatedness-of-all-life-an-illustration-from-richard-dawkins/

I also had some of the basic evidence (fossil records, observed mutations and natural selection, vestigial organs, junk DNA, and those now-discredited drawings of embryos). So, I wouldn’t have won a debate on evolution, but I had the basic idea. More importantly, everyone took it for granted. Criticism of Darwin’s theory of evolution was unheard of in the schools I attended.

Enter college: As a freshman in college, I hear about people who didn’t believe in evolution for the first time. It was mind boggling. Evolution is supposed to be true. My biology textbook said so. My story is tragic from there onwards. I tried to look at the evidence for and against evolution. It could have gone better. Here I was being told by ‘creationists’ and ‘Intelligent Design advocates’ that the fossil record has gaps, microevolution has been proven but not macroevolution, there are limits to biological change, there really isn’t good evidence for macroevolution, microbiology pokes holes in Darwin’s theory, etc. etc. I also received the groundbreaking news that Hackel’s drawings of embryos were staged (!!!) and the Miller Urey experiment has been discredited. Oh, golly.

On the other side, supporters of the theory of evolution were telling me that there are gobs of evidence for evolution like evolved viruses, and the fossil record and evolution has been observed in the lab and anybody who doubts evolution is either stupid, ignorant, uninformed, insane or wicked, etc. (please fill in the other insults you’ve heard).

So I was completely turned off. The debate is too charged. One side is too rude and uninterested in discussion. I don’t even really care about it anymore. Whenever someone asks me what I think about evolution, I tell them that I don’t know. If they laugh at me, I get away from them. There’s no point talking with people who don’t want to talk. That’s my problem with evolution – the people who support it.

I don’t fancy myself inexcusably ignorant or stupid or insane or wicked. I’m just an eighteen year old who covered everything but evolution in high school. My knowledge of the theory isn’t worse than that of the trolls on Youtube who accept it. But I don’t believe in evolution. I won’t until I have good reason to. I don’t have another explanation for the complexity of life on earth, but I don’t have to.

Over the next few days I might try to work through some of the evidence for Darwin’s theory of evolution. Or I might just watch Ugly Betty and do homework. The show is disgusting, but good for passing time.

EDIT: After some thought, I believe we did cover evolution in Social Studies during my first three years of secondary school. That explains why the memory is so fuzzy.

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* Complete list:
Junior Secondary School: English, Math, Integrated Science, Social Studies, Music, Fine Art, Edo language, French, Business Studies, Agricultural Science, Computer Science, Physical and Health Education, Introductory Technology, Home Economics, Christian Religious Studies
Senior Secondary: English, Math, Further Math, Biology, Physics, Chemistry, Geography, Computer Science, Agricultural Science