Mike Riddle: Does Evolution Have a . . . Chance?

It's all very well to have a degree in mathematics and try and calculate the probability for proteins forming, but if you don't know - or choose to ignore - the current models of how new proteins are made, and instead use your own naîve model involving everything at random, then no wonder you get a very small probability.

But I'm getting ahead of myself. I just read (don't know why, really) an article by Mike Riddle, President of the Creation Training Initiative:

Does Evolution Have a . . . Chance?

Here's the whole things with my comments in red.

One has only to contemplate the magnitude of this task to concede that the spontaneous generation of a living organism is impossible. Yet we are here—as a result, I believe, of spontaneous generation.1
—George Wald, Nobel Laureate

In today’s culture, molecules-to-man evolution is being taught as a fact, even though it is known to “go against the odds.” But few realize the odds they are up against! And they are immense! 

The Bible teaches that God is the Creator of all things (Genesis 1; Colossians 1:16; John 1:1–3; Revelation 4:11). While these passages rule out any possibility of Darwinian evolution, they do allow for variation within a created kind. But there is much opposition to what the Bible teaches. People holding to evolution would argue that random chance events, natural selection, and billions of years are sufficient to account for the universe and all life forms. The fact they they rule out evolution merely means that they are wrong. Evolution - including macroevolution - has been observed.

Do You Believe in “Magic”?

Most people recognize “magic” as an illusionary feat or trickery by sleight of hand. But how far are you willing to go to believe something can happen by “dumb luck” or chance? For example, if I were to role a die and have it come up six three times in a row, would you consider that lucky? How about if I rolled six ten times in a row? Now you might suspect that I am using some trickery or that the die is weighted. It is much more incredulous to believe chance as an explanation than the magic of creationism. (Also, [sic]).

How far are we willing to go to accept something as a chance occurrence or before we recognize that it was just an illusion? We can test this by measuring our credulity factor. Credulity is the willingness to believe something on little evidence.

Measuring Our Credulity Factor against Evolution

Evolutionists state that life originated by natural processes about 3.8 billion years ago. Is there any evidence for this happening? Freeman Dyson, theoretical physicist, mathematician, and member of the U.S. National Academy of Sciences states:

Concerning the origin of life itself, the watershed between chemistry and biology, the transition between lifeless chemical activity and organized biological metabolism, there is no direct evidence at all. The crucial transition from disorder to order left behind no observable traces.2

Since the origin of life has never been observed, this is a major hurdle! Yes, true. It is a darned annoying fact that we cannot directly observe anything that happened in the past. If only we could directly observe murderers in the act, then detective work would be much easier. We are left with the question, “Is the origin of life by naturalistic processes possible?” This can, in part, be tested by examining two areas:

1. The success of scientists in creating life or the components of a living cell.
2. The probability that such an event could occur.

We are not really "left with the question" of the origin of life (aka abiogenesis) if we are concerned with evolution. Suppose for a moment that God created life initially - this doesn't rule out evolution following that. Those two things are quite distinct, and even though natural selection plays an important role in abiogenesis, the scientists who work on abiogenesis are different that those who work on evolution, because they require very different areas of expertise. So, if we could never find a scientific solution to abiogenesis, that wouldn't mean that we cannot understand evolution as a natural process (which we do).
The Structural Unit of Living Organisms—The Cell

Cells are made up of thousands of components. One of these components is protein. Proteins are large molecules made up of a chain of amino acids. In order to get a protein useful for life, the correct amino acids must be linked together in the right order. There are of course many different ways to put together proteins that are useful for life. How easy is this and does it happen naturally? It turns out that this is not an easy process. No, not if your "process" is random chance with nothing else. There are large hurdles that evolutionary processes must overcome in order to build a biological protein.

Protein molecules contain very specific arrangements of amino acids. Even one missing or incorrect amino acid can lead to problems with the protein’s function. Yes, some amino acid changes will mess with protein function, but many changes are neutral and do not change protein function.

Making Mathematics Painless

Before applying mathematics and probability to the origin of life, we need to consider seven parameters that will affect the formation of a single protein.

First, there are over 300 different types of amino acids. However, only 20 different amino acids are used in life. This means that in order to have life, the selection process for building proteins must be very discriminating. But it didn't necessarily have to be this discriminating in the beginning. 

Second, each type of amino acid molecule comes in two shapes commonly referred to as left-handed and right-handed forms. Only left-handed amino acids are used in biological proteins; however, the natural tendency is for left- and right-handed amino acid molecules to bond indiscriminately.

Third, the various left-handed amino acids must bond in the correct order or the protein will not function properly.3 Again, there is not one correct protein, but a lot of variation, and proteins that doesn't work for one thing can work for another.

Fourth, if there was a pond of chemicals (“primordial soup”), it would have been diluted with many of the wrong types of amino acids and other chemicals available for bonding, making the proper amino acids no longer usable. This means there would have been fewer of the required amino acids used to build a biological protein. But there could have been enough. Plus, the twenty that are currently used could have been a function of those being to most abundant ones. 

Fifth, amino acids require an energy source for bonding.4 Raw energy from the sun needs to be captured and converted into usable energy. Where did the energy converter come from? It would require energy to build this biological machine. However, before this energy converter can capture raw energy, it needs an energy source to build it—a catch-22 situation.5 See the video below. 

Sixth, proteins without the protection of the cell membrane would disintegrate in water (hydrolysis), disintegrate in an atmosphere containing oxygen, and disintegrate due to the ultraviolet rays of the sun if there was no oxygen present to form the protective ozone layer.6

Seventh, natural selection cannot be invoked at the pre-biotic level. The first living cell must be in place before natural selection can function. No, selection works on anything that replicates. Self-replicating molecules like ribozymes are used in laboratory experiments. They are affected by natural selection.

Considering all seven of these hurdles, how probable is it that a single protein could have evolved from a pool of chemicals? Probability outcomes are measured with a value ranging from zero through one. The less likely an event will happen, the smaller the value (closer to zero). The more likely an event will occur, the larger the value (closer to one). Wow, talk about dumbing it down! If you know nothing about the natural processes that are involved, then it does seem very unlikely. But do watch this video to learn one or two things about those processes:

Let’s practice this using a coin. What are the chances of getting a heads when we flip a penny? The answer is 50 percent, or one chance in two (written 1/2). What is the chance of getting two heads in a row? Since each toss is 1/2 we can multiply each occurrence to get the final probability. This would be 1/2 x 1/2 which would equal 1/4 (or one chance in four). Now let’s use some bigger numbers.

When we flip a coin we have two possible outcomes, heads or tails. In this problem, we want to calculate the probability of getting all heads every time we flip a coin. We can use this exercise to test our credulity factor. How many heads in a row are we willing to accept as a chance occurrence? At what point would we suspect an illusion or some form of magic (trickery)? We wouldn't expect magic. Ever. Only godbots do that. We would instead expect some other natural process being involved.

The objective of using probabilities is to demonstrate the probability or chance of getting a certain result. On average, how many times and how often will we need to flip the coin to achieve 100 heads in a row? Over 300 million times a second for over one quadrillion years! If you could only do one trial at a time, then that would take a long time. But if you can do many at the same time in parallel, then you could get one hundred heads very quickly. If we could run just a billion such trials in parallel, then it would only take a million years, which is not long on geological time-scales. (Also, that number is slightly wrong. Only a little over 40 million times per second is needed for a quadrillion (10¹⁵) years. - My math is better than yours so I win!!! ;P)

The chances of getting all heads 100 times in a row is similar to the chance of getting 100 left-handed amino acids to form a biological protein. Proteins range in size from about 50 to over 30,000 amino acids. To get a small protein of 100 left-handed amino acids from an equal mixture of left- and right-handed amino acids, the probability would then be 1030 or 1 followed by 30 zeros (1,000,000,000,000,000,000,000,000,000,000). But but but, this is assuming that the process is random (again, it isn't - see the video above). How believable (credulity factor) is it that this could happen by random chance? Also, consider that this has never been observed! We all agree that it hasn't been observed, but we all agree that things that haven't been observed have taken place, right? Like a fallen tree in the forest is assumed to have fallen, even though no one were there to observe it. Chance protein formation has always been accepted as a matter of faith by evolutionists. No, not chance formation. Again, again, see the video. You are ignoring the natural processes that can explain these things.

Number of desired heads in a row	Probability	Number of flips	Credulity factor (chance)
1	1/2 have	2	Yes / No
2	1/4 (1/22)	4	Yes / No
3	1/8 (1/23)	8	Yes / No
4	1/16 (1/24)	16	Yes / No
5	1/32 (1/25)	32	Yes / No
8	1/256 (1/28)	256	Yes / No
10	1/1024 (1/210)	1024	Yes / No
20	1/1,048,576 (1/220)	1,048,576	Yes / No
100	1/1030(1/2100)	1 followed by 30 zeros	Yes / No

Ten is pretty good! We can work with ten. Not that we thereby admit that Riddle's puerile model here is the correct one (cause it isn't), but suppose to have a bunch of string of ten heads in a row, then those could be assembled together three at a time to make strings of 30 heads in a row.

But wait, there is more! This number, 1030, only measures the possibility of getting all left-handed amino acids. It does not say anything about their order. In our example, we have a chain of 100 amino acids. Each position can be occupied by any 1 of 20 different amino acids common to living things, and these must be in a specific order to form a functional protein. What is the probability that the correct amino acid will be placed in position number 1 of the chain? It will be 1/20. What is the probability that the first two positions will be correct? This can be calculated by multiplying the two probabilities together (1/20 x 1/20 = 1/202). Therefore, the probability of getting all 100 amino acids in the correct position would be 1/20 multiplied by itself 100 times or 1/20100 (this equates to 1/10130). This is 1 followed by 130 zeros! Which is not how proteins are thought to have formed. See the video above. This is like me saying that the process by which the Bible is written is by randomly stringing letters together. There are 3,566,480 letters in the bible (Bing it yourself), so with 26 different letters that gives a chance of one in 26^3566480. This is 1 followed by more than 5 million zeros! Therefore the Bible could not have been written by random chance. - Point here being that that is of course not the process by which the Bible was written, just as proteins of length 100 are not assembled by chance.

Large numbers can be hard to visualize or even comprehend. To put this in picture format we can use a smaller number 1021 (1 followed by 21 zeros). If we were to take 1021 silver dollars and lay them on the face of the earth; they would cover the entire land surface to a depth of 120 feet.7

Are there upper limits for which we can logically expect an event will not occur by random chance? The mathematician Emile Borel proposed 1/1050 as a universal probability bound. This means that any specified event beyond this value would be improbable and could not be attributed to chance.8 Repeat after me: scientists do not attribute random chance to the formation or proteins.

As we can see, the probability of getting a single small protein (1/10130) far exceeds this limit. Even if the protein can interchange amino acids at various positions (such as in the case of the protein cytochrome a),9 the resulting probability still exceeds the limit of 1/1050. So far we have only looked at the probability of getting a single small protein by random chance. What are the chances of getting all the proteins necessary for life? By chance? Negligible. Relevance...? 

No matter how large the environment one considers, life cannot have had a random beginning . . . there are about two thousand enzymes, and the chance of obtaining them all in a random trial is only one part in (1020)2000 = 1040,000, an outrageously small probability that could not be faced even if the whole universe consisted of organic soup.10

Let our conclusion be that life did not have a random beginning (that is, completely random, as described here). 

This number is so large (1 followed by 40,000 zeros) that it staggers the imagination how life could have evolved by natural, random processes. Yet, people continue to hold onto their belief that life did evolve by random chance (high credulity factor). Yes, staggering, I tell you. If you only rely on random processes, which scientists do not. Watch the video above!

Time is in fact the hero of the plot. . . . What we regard as impossible on the basis of human experience is meaningless here. Given so much time, the “impossible” becomes possible, the possible probable, and the probable virtually certain. One has only to wait: time itself performs the miracles.11

This statement attributes supernatural qualities to time! It also allows for anything to happen. This means we are no longer bound by the laws of science or any other natural limits. The statement thus becomes meaningless. You are the one not bound by the laws of science when you think the science says it is all random chance.

Tricks of the Trade

Since scientists have been unable to create life, they are forced to speculate through research and sometimes “sleight of hand” how it might have arrived on earth. Below are some of the tricks of the trade used to avoid the obvious—that God is the Creator of all things (Colossians 1:16). God or Allah or Odin or Zeus or Baal, or whatever. False dichotomy. Also, "speculate though research." *chortle* No, even if we understand natural processes that can create life, we can never know for sure how it actually happened, because all evidence of it has been erased. There are no fossils or anything else left from back then that we can take a direct look at. Too bad. But we can make very informed models by which we can understand abiogenesis. Sorry if this offends your religious sensibilities.

1. It happens naturally

“The formation of biological polymers from monomers is a function of the laws of chemistry and biochemistry, and these are decidedly not random.”12 This is a link to a great discussion on the probability of abiogenesis on TalkOrigins. It is also from 1998, and we have learned a lot since then. See, for example, the video above.

Explanation

This is an incorrect statement. I see nothing incorrect about it! Those laws are really not random!!! If it happens naturally, then why can’t scientists duplicate this in the lab? See video above. Amino acids do not spontaneously bond together to make proteins. First, it takes a source of energy to do this. The Sun or geothermal energy. Second, the natural tendency is to bond left- and right-handed amino acids, but life requires all left-handed amino acids. Third, they must be in the correct order or the protein will not function properly. Fourth, it requires the instructions of DNA to get the right amino acids. Where did DNA come from? Fifth, protein molecules tend to break down in the presence of oxygen or water. For answer to all of these, see the video above.

2. The deck of 52 cards

In a deck of 52 playing cards there are almost 1068 possible orderings of the cards. If we shuffle the deck we can conclude that the possible ordering of the cards having occurred in the order we got is 1 chance in 1068. This is certainly highly improbable, but we did come up with this exact order of cards. Therefore, no matter how low the probability, events can still occur and evolution is not mathematically impossible.

Explanation

In this example the math is correct but the interpretation is wrong. Your interpretation of your math is what's wrong here. If the arrangement had been specified beforehand, then the actual outcome would be surprising. By shuffling the cards, the probability is one that a sequence will occur. The fallacy is that the order is predicted after the fact. Your fallacy is that you assumed that there is just one correct protein, and is contains a hundred amino acids. That is false.

3. All the people

We are in a room of 100 people. What is the probability that all 100 people would be here in this room at this exact time? The probability is enormous, but yet we are all here.

Explanation

Two things are wrong with this reasoning. First, the people were not pre-specified. This is another example of an after-the-fact prediction. Second, each person made a decision to attend; therefore, this is not a chance gathering. This turns out to be a misunderstanding between a chance event and intelligent choice. Right! Just like proteins are not chance gatherings. There are natural non-random processes involved. I think you are getting it now.

4. Probability is not involved

Probability has nothing to do with evolution because evolution has no goal or objective.

Explanation

This statement disagrees with modern biology textbooks. Agreed. Probability does have something to do with it. I don't know where the quote in point 4 comes from (it isn't in the TalkOrigins article). It's just your probability calculations that have the wrong premises, namely ignoring lots of natural processes.

When there is more than one possible outcome and the outcome is not predetermined, probability can become a factor. In the case of evolution there is no pre-assigned chemical arrangement of amino acids to form a protein. Right again! (Yeah!) There are indeed not only one possible outcome, but many proteins that could work. Therefore, the formation of a biological protein is based on random chance. No, that really doesn't follow. I thought for a moment you were with us, but science lost you again. Scientists know today that it is only because of the instructions (information) in DNA that only left-handed amino acids are linked in the proper order. 

Cells link amino acids together into proteins, but only according to instructions encoded in DNA and carried in RNA.13

Both creationists and evolutionists agree that DNA is essential for linking the correct amino acids in a chain to form a protein. The unanswered question is, “Where and how did DNA acquire the enormous amount of information (instructions) to form a protein?” There is no known natural explanation that can adequately explain the origin of life, or even a single protein. Yes there is. See the vid... The evolutionists are then left to rely on the odds (chance) that such a tremendous, improbable event occurred. No, there are other processes. zomg! Molecular biologist Michel Denton puts the event in perspective:

Is it really credible that random processes could have constructed a reality, the smallest element of which—a functional protein or gene—is complex beyond our own creative capacities, a reality which is the very antithesis of chance, which excels in every sense anything produced by the intelligence of man?14

But wait, there is still more!

The Human Body, Time, and Evolution

It is estimated that the human body is made up of 60 trillion cells (60,000,000,000,000).15 How long would it take to just assemble this many cells, one at a time and in no particular order at the rate of: What the fuck does this have to do with anything?!? Who thinks that the human body is assembled one cell at a time? Also, this doesn't seem to have anything to do with evolution, but development - a process that we can and have observed directly.

One per second	1.9 million years
One per minute	114 million years
One per hour	6.8 billion years

These ages assume no mistakes! However, the evolutionary mechanism is based upon random errors (mistakes) in the DNA. Also included in assembling all the 60 trillion cells is that they have to make the right organs which all have to interact. Relevance?

The human body contains more than 40 billion capillaries extending over 25,000 miles, a heart that pumps over 100,000 times a day, red blood cells that transport oxygen to tissues, white blood cells that rush to identify enemy agents in the body and mark them for destruction, eyes and ears that are more complex than any man-made machine, a brain that contains over 100 trillion interconnections, plus many other parts such as the nervous system, skeleton, liver, lungs, skin, stomach, and kidneys. Relevance?

The complexity and dimensions of the human body are staggering. The probability of assembling 60 trillion cells that form specific organs that all work together to form a single human being in the evolutionary time scale of 3.8 billion years is a giant leap of faith. However, an all-knowing, all-powerful Creator has told us in His Word that He is the designer. That's not how anybody thinks the human body develops!

The hearing ear and the seeing eye, The Lord has made them both (Proverbs 20:12).

Every human body is a testimony to a purposeful Creator. As Malcolm Muggeridge said:

One of the peculiar sins of the twentieth century which we’ve developed to a very high level is the sin of credulity. It has been said that when human beings stop believing in God they believe in nothing. The truth is much worse: they believe in anything.16

Nonsense! Both statements are false. I believe in many things, and God is not one of them. 

Conclusion

Probability arguments can present a strong argument for the existence of a Creator God. The probability arguments presented here - even if they were based on sound assumptions, which they aren't - argues nothing for the existence of a Creator God. Certainly not any particular God. Maybe FSM. However, even when such evidence is presented to an evolutionist there is no guarantee that he or she will be persuaded. No, immature arguments like these persuade no scientists. Creationists, maybe. The real issue is not about evidence If you admit that you think it has nothing to do with evidence, why are you going through all these exercises in the first place?; it is a heart issue. As Christians we are called to have ready answers and break down strongholds that act as stumbling blocks to the unbeliever. It is the Holy Spirit that changes lives.

But sanctify the Lord God in your hearts, and always be ready to give a defense to everyone who asks you a reason for the hope that is in you, with meekness and fear (1 Peter 3:15).

For the weapons of our warfare are not carnal but mighty in God for pulling down strongholds, casting down arguments and every high thing that exalts itself against the knowledge of God, bringing every thought into captivity to the obedience of Christ (2 Corinthians 10:4–5).

Your real creationist weapon is ignorance - something that you rely heavily on when calculating probabilities for protein formation by random chance alone.

Footnotes

1. George Wald [biochemist and winner of Noble Prize in Physiology or Medicine, 1967], “The Origin of Life,”Scientific American 191 no. 48 (1954): 46.
2. Freeman Dyson, Origins of Life (New York, NY: Cambridge University Press, 1999), p. 36.
3. “The order of the amino acids in a protein determines its function and whether indeed it will have a function at all.” Lee Spetner, Not By Chance (New York, NY: Judaica Press, 1997), p. 31.
4. “The important fact that amino acids do not combine spontaneously, but require an input of energy, is a special problem.” Charles Thaxton, Walter Bradley, and Roger Olsen, The Mystery of Life’s Origin (Dallas, TX: Lewis and Stanley, 1992), p. 55.
5. “A source of energy alone is not sufficient, however, to explain the origin or maintenance of living systems. The additional crucial factor is a means of converting this energy into the necessary useful work to build and maintain complex living systems.” Thaxton, Bradley, and Olsen, The Mystery of Life’s Origin, p. 124.
6. “What we have then is a sort of ‘catch 22’ situation. If we have oxygen we have no organic compounds, but if we don’t have oxygen we have none either.” Michael Denton, Evolution: A Theory in Crisis (Bethesda, MD: Adler and Adler, 1985), p. 262.
7. Peter Stoner, Science Speaks (Wheaton, IL: Van Kampen Press, 1952), p. 75.
8. Emile Borel, Probabilities and Life (New York, NY: Dover, 1962), p. 28.
9. A transport protein involved in the transfer of energy (electrons) within cells.
10. Sir Fred Hoyle and Chandra Wickramasinghe, Evolution from Space (London: Dent, 1981), p. 148, 24.
11. George Wald, “The Origin of Life,” p.48.
12. Ian Musgrave, “Lies, Damned Lies, Statistics, and Probability of Abiogenesis Calculations,” TalkOrigins, www.talkorigins.org/faqs/abioprob/abioprob.html.
13. G.B. Johnson, Biology: Visualizing Life (Austin, TX: Holt, Rinehart, and Winston, 1998), p. 193.
14. Denton, Evolution: A Theory in Crisis, p. 342.
15. Boyce Rensberger, Life Itself (New York, NY: Oxford University Press, 1996), p. 11.
16. Malcolm Muggeridge, “An Eighth Deadly Sin,” Woman’s Hour radio broadcast, March 23, 1966. Quoted in Malcolm Muggeridge and Christopher Ralling, Muggeridge Through the Microphone: B.B.C. Radio and Television(London: British Broadcasting Corporation, 1967).

The simulations behind the fitness landscape visualizations

We now have two videos out featuring evolving populations in two-dimensional fitness landscapes.

Using fitness landscapes to visualize evolution in action Youtube Vimeo
Visualizing coevolution in dynamic fitness landscapes Youtube Vimeo

(Best to watch the first one first for some background information about fitness landscapes.)





These movies are based on simulations of organisms evolving by reproduction, mutation and selection. Populations move around on a map that depict fitness as a function of phenotype (i.e., the biological and physical characteristics of an individual organism).

The following is a semi-technical description of the simulations, so be warned. If you have questions about some details, let me know in the comments.

Phenotype. The fitness landscapes that you see are phenotype-fitness maps. That means that for each possible phenotype there is an associated fitness value (which is a scalar - a single number). The phenotype of these simulated organisms consist of two traits. Both of these traits are numbers that range between 1 and 200. A phenotype of (10, 10) means that the organisms is situated near the lower corner of the fitness landscape, and a phenotype of (195, 3) means that the organism is situated near the right corner.

Sympatry. All simulations shown in the videos have no spatial component. The moving around in the landscape is only caused by changes in the phenotype, not geographically, and the population is therefore said to be strictly sympatric or well-mixed. If the individual organisms did move around in physical space, then where they are located relative to each other could have an influence of who they interact with, which could change things further. Structured populations are known to affect evolutionary dynamics through social interaction, competition for resources, and mating.

Mutations in these simulations work like this: Each of the two traits mutate at a set mutation rate. Every time an organisms reproduces, the new organism has a chance to mutate which is equal to the mutation rate. This is true for each trait, so that a mutation rate of 0.05 means that trait 1 has a 5% chance of changing, and trait 2 also has a chance of changing. These two events are independent of each other. When a trait mutates, the trait value is either increased or decreased by one. In other words, if the trait value of the parent was 142, the offspring will have a value of 141 or 143 with equal probability. There is no underlying genetics in these models, and the phenotype is directly inherited.

Selection.  Organisms reproduce asexually. Every offspring is a clone of the parent, except for any mutations. Every computational update some organisms die and some reproduce. Death is completely random, so that every organism has an equal chance or being removed every update. Who gets to reproduce is also random, but fitness affects this chance. For example, an organism that has twice the fitness of another organisms has a probability of reproducing that is twice as high. This doesn't guarantee that it will have twice as many offspring - but on average it will be approximately so.

Population size. Competition in these simulations is for space. Some simulations have a constant population size. In this case, a small percentage of the population is killed every update, and those empty spots are filled by selecting among the survivors. Other simulations have variable population sizes. In these vases every surviving organism has a chance to reproduce once every computational update that is equal to their normalized fitness. The variable population size simulations results in stable populations where the population size fluctuate around a value which is ultimate given by the average fitness. For example, when the population climbs a peak the average fitness of organisms increases, and the average chance of reproducing goes up. This means that the population grows in size. The way this is implemented is such that there is a carrying capacity set to 2,000 individuals. If the population reaches this size, 50% are moved next update, and the other 50% then has a chance to reproduce. If they all had the maximum fitness (a set value), then they would all reproduce, and the population size would be back to 2,000. This doesn't happen, because mutations would make some individuals have a fitness lower than the maximum. If the population size gets very low, the number than is killed every update is set to less than 50%, so that more than half of the organisms survives. The precise fraction killed goes from zero at population size zero linearly through 50% at 2,000. This most often results in population of around 1,600 organisms. Most published simulations studies of evolution use constant population sizes.

Dynamic landscapes. In the second video of coevolution systems the fitness landscape of one population changes over time because they are affected by another population. In the moth-orchid simulation, the length of the moth proboscis needs to be longer than the orchid spur length to be able to get to the nectar at the bottom. If every individual orchid has a spur that is longer than the proboscis, then moth fitness is low (but non-zero). Having a proboscis that is as long as the spurs of half of the orchid population will give the moth an intermediate fitness. The fitness landscape of the orchids is similarly affected by the moth population, with the orchids needing spurs that are longer than the proboscis in order for the feeding moth to get pollen on their faces. This drives the evolution of longer proboscises and spurs as dictated by the two changing fitness landscapes. In the rock-paper-scissors simulation, the fitness landscape of each population is affected by the phenotype values of the other two populations.

How the woman got her period

Guest post by Suzanne Sadedin. This is reposted from Quora.

Suzanne got her PhD in biology from Monash University, and has done postdoctoral research at Monash University, University of Tennessee, Harvard University, and KU Leuven.

What is the evolutionary benefit or purpose of having periods?

 I'm so glad you asked. Seriously. The answer to this question is one of the most illuminating and disturbing stories in human evolutionary biology, and almost nobody knows about it. And so, O my friends, gather close, and hear the extraordinary tale of:

HOW THE WOMAN GOT HER PERIOD

Contrary to popular belief, most mammals do not menstruate. In fact, it's a feature exclusive to the higher primates and certain bats*. What's more, modern women menstruate vastly more than any other animal. And it's bloody stupid (sorry). A shameful waste of nutrients, disabling, and a dead giveaway to any nearby predators. To understand why we do it, you must first understand that you have been lied to, throughout your life, about the most intimate relationship you will ever experience: the mother-fetus bond.

Isn't pregnancy beautiful? Look at any book about it. There's the future mother, one hand resting gently on her belly. Her eyes misty with love and wonder. You sense she will do anything to nurture and protect this baby. And when you flip open the book, you read about more about this glorious symbiosis, the absolute altruism of female physiology designing a perfect environment for the growth of her child.

If you've actually been pregnant, you might know that the real story has some wrinkles. Those moments of sheer unadulterated altruism exist, but they're interspersed with weeks or months of overwhelming nausea, exhaustion, crippling backache, incontinence, blood pressure issues and anxiety that you'll be among the 15% of women who experience life-threatening complications.

From the perspective of most mammals, this is just crazy. Most mammals sail through pregnancy quite cheerfully, dodging predators and catching prey, even if they're delivering litters of 12. So what makes us so special? The answer lies in our bizarre placenta. In most mammals, the placenta, which is part of the fetus, just interfaces with the surface of the mother's blood vessels, allowing nutrients to cross to the little darling. Marsupials don't even let their fetuses get to the blood: they merely secrete a sort of milk through the uterine wall. Only a few mammalian groups, including primates and mice, have evolved what is known as a “hemochorial” placenta, and ours is possibly the nastiest of all. 

Inside the uterus we have a thick layer of endometrial tissue, which contains only tiny blood vessels. The endometrium seals off our main blood supply from the newly implanted embryo. The growing placenta literally burrows through this layer, rips into arterial walls and re-wires them to channel blood straight to the hungry embryo. It delves deep into the surrounding tissues, razes them and pumps the arteries full of hormones so they expand into the space created. It paralyzes these arteries so the mother cannot even constrict them.

What this means is that the growing fetus now has direct, unrestricted access to its mother's blood supply. It can manufacture hormones and use them to manipulate her. It can, for instance, increase her blood sugar, dilate her arteries, and inflate her blood pressure to provide itself with more nutrients. And it does. Some fetal cells find their way through the placenta and into the mother's bloodstream. They will grow in her blood and organs, and even in her brain, for the rest of her life, making her a genetic chimera.

This might seem rather disrespectful. In fact, it's sibling rivalry at its evolutionary best. You see, mother and fetus have quite distinct evolutionary interests. The mother 'wants' to dedicate approximately equal resources to all her surviving children, including possible future children, and none to those who will die. The fetus 'wants' to survive, and take as much as it can get. (The quotes are to indicate that this isn't about what they consciously want, but about what evolution tends to optimize.)

There's also a third player here – the father, whose interests align still less with the mother's because her other offspring may not be his. Through a process called genomic imprinting, certain genes inherited from the father can activate in the placenta. These genes ruthlessly promote the welfare of the offspring at the mother's expense.

How did we come to acquire this ravenous hemochorial placenta which gives our fetuses and their fathers such unusual power? Whilst we can see some trend toward increasingly invasive placentae within primates, the full answer is lost in the mists of time.

Uteri do not fossilize well.

The consequences, however, are clear. Normal mammalian pregnancy is a well-ordered affair because the mother is a despot. Her offspring live or die at her will; she controls their nutrient supply, and she can expel or reabsorb them any time. Human pregnancy, on the other hand, is run by committee – and not just any committee, but one whose members often have very different, competing interests and share only partial information. It's a tug-of-war that not infrequently deteriorates to a tussle and, occasionally, to outright warfare. Many potentially lethal disorders, such as ectopic pregnancy, gestational diabetes, and pre-eclampsia can be traced to mis-steps in this intimate game. 

What does all this have to do with menstruation? We're getting there.

From a female perspective, pregnancy is always a huge investment. Even more so if her species has a hemochorial placenta. Once that placenta is in place, she not only loses full control of her own hormones, she also risks hemorrhage when it comes out. So it makes sense that females want to screen embryos very, very carefully. Going through pregnancy with a weak, inviable or even sub-par fetus isn't worth it.

That's where the endometrium comes in. You've probably read about how the endometrium is this snuggly, welcoming environment just waiting to enfold the delicate young embryo in its nurturing embrace. In fact, it's quite the reverse. Researchers, bless their curious little hearts, have tried to implant embryos all over the bodies of mice. The single most difficult place for them to grow was – the endometrium.

Far from offering a nurturing embrace, the endometrium is a lethal testing-ground which only the toughest embryos survive. The longer the female can delay that placenta reaching her bloodstream, the longer she has to decide if she wants to dispose of this embryo without significant cost. The embryo, in contrast, wants to implant its placenta as quickly as possible, both to obtain access to its mother's rich blood, and to increase her stake in its survival. For this reason, the endometrium got thicker and tougher – and the fetal placenta got correspondingly more aggressive.

But this development posed a further problem: what to do when the embryo died or was stuck half-alive in the uterus? The blood supply to the endometrial surface must be restricted, or the embryo would simply attach the placenta there. But restricting the blood supply makes the tissue weakly responsive to hormonal signals from the mother – and potentially more responsive to signals from nearby embryos, who naturally would like to persuade the endometrium to be more friendly. In addition, this makes it vulnerable to infection, especially when it already contains dead and dying tissues.

The solution, for higher primates, was to slough off the whole superficial endometrium – dying embryos and all – after every ovulation that didn't result in a healthy pregnancy. It's not exactly brilliant, but it works, and most importantly, it's easily achieved by making some alterations to a chemical pathway normally used by the fetus during pregnancy. In other words, it's just the kind of effect natural selection is renowned for: odd, hackish solutions that work to solve proximate problems. It's not quite as bad as it seems, because in nature, women would experience periods quite rarely – probably no more than a few tens of times in their lives between lactational amenorrhea and pregnancies**.

We don't really know how our hyper-aggressive placenta is linked to the other traits that combine to make humanity unique. But these traits did emerge together somehow, and that means in some sense the ancients were perhaps right. When we metaphorically 'ate the fruit of knowledge' – when we began our journey toward science and technology that would separate us from innocent animals and also lead to our peculiar sense of sexual morality – perhaps that was the same time the unique suffering of menstruation, pregnancy and childbirth was inflicted on women. All thanks to the evolution of the hemochorial placenta.

Links:
The evolution of menstruation: A new model for genetic assimilation
Genetic conflicts in human pregnancy
Menstruation: a nonadaptive consequence of uterin... [Q Rev Biol. 1998]
Natural Selection of Human Embryos: Decidualizing Endometrial Stromal Cells Serve as Sensors of Embryo Quality upon Implantation
Scientists Discover Children’s Cells Living in Mothers’ Brains

Credits: During my pregnancy I was privileged to audit a class at Harvard University by the eminent Professor David Haig, whose insight underlies much of this research. Thanks also to Edgar A. Duenez-Guzman, who reminded me of crucial details. All errors are mine alone.

*Dogs undergo vaginal bleeding, but do not menstruate. Elephant shrews were previously thought to menstruate, but it's now believed that these events were most likely spontaneous abortions.

**One older published estimate for hunter gatherers was around 50, but this relied on several assumptions that suggest it's a significant overestimate. In particular, it includes 3 whole years of menstruation before reproduction (36 periods) for no obvious reason.

We can make an estimate from studies of the Hadza of Tanzania, who reach puberty around 18, bear an average of 6.2 children in their lives (plus 2-3 noticeable miscarriages) starting at 19, and go through menopause at about 43 if they survive that long (about 50% don't). Around 20% of babies die in their first year; the remainder breastfeed for about 4 years. So this is 25 years of reproductive life, of which about 20 are spent lactating, and 4.5 pregnant. That would leave only about 6 periods, but amenorrhoea would cease during the last year of lactation for each child, so this figure is too low. On the other hand, this calculation ignores the ~50% of women who died before menopause, miscarriages, months spent breastfeeding infants who would die, and periods of food scarcity, all of which would further reduce lifetime menstruation. Stats from: http://www.fas.harvard.edu/%7Ehb...