Tag Archives: Natural Selection

Evolution in a Deck of Cards

dnaFor some people the process of evolution is a difficult concept to grasp. For sure, evolution is a counter-intuitive idea. We don’t experience evolution in our daily lives. It only makes sense when we look beyond the surface of things; evolutionary concepts require a long-term view. Perhaps the biggest stumbling block towards understanding evolution is the disconnection between our lives and the evolutionary timeline. If we compared the history of the Earth to the length of a person’s arm, all of human history could be wiped out with a single stroke of a nail file.

Still, despite much scientific evidence for evolution, many people are not convinced. They may look for supernatural explanations for the existence of life, or conclude the question is beyond human understanding. How is it possible that all life evolved from single cell organisms? How did even a single cell evolve? And how did life diversify into millions of species? To get a grasp for evolution we need to shift our attention from the finished product to the process.

Evolution is indeed a process, which is ongoing. And it has no finished product in mind. Evolution can be defined as gradual changes and development over time. However, there is a mechanism that generates those changes, which Darwin called natural selection. Perhaps Darwin’s greatest insight was recognizing the power of natural selection. It is similar to an algorithm, because nature selects positive survival and reproductive traits. It also discards negative survival and reproductive traits. The process is cumulative and continuous from generation to generation. Once the process began improvements to life were inevitable, even though specific outcomes were not guaranteed.

The Card Game

deck-of-cardsAs a thought experiment we can use the analogy of a card game to show how natural selection works. The analogy is not perfect, because there are subtleties in evolution that are more complicated. The exercise is meant to provide a simple analogy for natural selection.

Although it was not known in Darwin’s time, we now understand that life is controlled by genetic information. Essentially, it is genes that are passed on through the generations. In our analogy it is more useful to view the cards as genes, and a hand of cards as a group of genes (or an individual life form). The game has 4 basic ground rules:

1) The deck of cards represents the gene pool: We need to assume multiple decks, because the same genes exist simultaneously in other individuals and are copied many times over. Each card carries information, which may or may not survive each reshuffling. For example, the 5 of spades is one gene and the 10 of harts is another gene.

2) The shuffling symbolizes the generations: Every time the cards are shuffled and handed out, it’s like a new generation. The cards are always being rearranged in different combinations.

3) The players act as natural environments: The players select which cards they want to keep. Just like nature favors different genes in different environments, each player will select different card combinations. In our game some players are playing poker, others cribbage and others bridge. For example, the poker player represents a specific environment, such as an ocean.

4) The goal of the game is to collect the best hand possible: Every player keeps the cards they want, and discards the ones they don’t want. The poker players will collect different card arrangements than the bridge players. But all the cards come from the same card pool. This selection process is done with every deal.

Stable Arrangements

For natural selection to work the process had to work in the primordial period. The creation of life on earth probably did not start in an instant of time. It is more likely that the building blocks (atoms and molecules) were assembling for a long time; nature was favoring stable patterns. Richard Dawkins points out in The Selfish Gene:

“The earliest form of natural selection was simply a selection of stable forms and a rejection of unstable ones.”

microscopic-lifeJust like today, things that last are stable arrangements of atoms (whether living or nonliving). Consequently, life began in a fuzzy period where forms were interacting and assembling. At some point the forms acquired the ability to replicate (with occasional errors). The errors are necessary for evolution; this would be like randomly adding new cards to the deck (like a 15 of diamonds). Eventually, simplicity grew into increased complexity; small patterns grew into larger patterns. This is also what happens with the game of cards.

Exact patterns would be difficult to recognize in the first few hands. Nevertheless, there would still be cards that are more desirable than others. Generally, an ace or a face card is better than a numbered card. But there are exceptions, which depends on the type of game and the combination of cards. With each reshuffling patterns will emerge, where eventually an onlooker could identify the game each player is playing. This is analogous to the time when stable patterns would be recognized and classified as organic life (that’s if someone where watching).

Reshuffling the Deck

We can now see how the process of reshuffling the deck, selecting and discarding the cards would work. It would not take too many hands to achieve almost perfection. Each player would select for their specific game, just like nature selects for its specific environment. All the hands would contain some of the same cards, but in different combinations. Nature mixes the genes in the same way.

cards-in-rowsThe power of natural selection is the continual selection and discarding process, which occurs at unfathomable timescales. Successful genes are kept from generation to generation, random gene mutations are added, and remixed in endless combinations. Only the best of the best survive the process. That is why an after-the-fact view of evolution can be deceiving. Incredible order can emerge without a design and a planned outcome.

Our card game never ends; the players are always looking to make improvements, no matter how small. Many poker players will end up with a Royal Flush (the best possible hand). Bridge hands will end up with every card of the same suit or all aces and face cards. This is where our analogy doesn’t quite measure up. In real life the environments constantly change, which drives evolution to adjust. It’s like occasionally changing some rules to each card game, which will force the players to change their hands.

I hope this thought experiment helps to conceptualize how evolution can accomplish a seemingly daunting task. The basics of natural selection are only a starting point towards understanding evolution. Evolution is a messy process of trial and error, an incalculable amount of trials and errors, which muddies the water. Yet the time involved is critical to the process (more than 3 billion years).

Knowledge of evolution is fundamental towards understanding all life on earth. The life sciences could not progress without it. Our own bodies function as a result of evolution and much of human behavior has evolutionary roots. It has been said that, “Evolution is not something you believe in; either you understand it, or you don’t.”

 

References: Richard Dawkins, The Selfish Gene (Oxford: Oxford University Press, First published 1976, Second edition 1989, 30th anniversary edition 2006).


 

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A Gene Centered View of Natural Selection

Natural selection was Darwin’s term for the mechanism of evolution. In the slow process of evolution nature selects which organisms adapt to their environments successfully (that are most successful at surviving and reproducing). But what is the unit of selection? Is it the species, group, individual or gene? At what level do natural environments shape the evolution of life? Could there be a blending of different units or is one dominant? For example, do species evolve as a consequence of group selection, or do groups evolve as a result of individual selection; or do genes ultimate control the process?

Richard DawkinsThese questions have been debated by biologists and academics for a long time. Richard Dawkins, with the publication of The Selfish Gene, sided on the gene centered camp. The idea of gene selection had been proposed in scientific papers: First by Bill Hamilton in 1964 and then by others, such as John Maynard Smith and Robert Trivers in the early seventies.

Published in 1976, The Selfish Gene placed gene selection into the public sphere by getting beyond the technical aspects of the scientific papers. Dawkins’ book was accessible to a general audience, and has been influential in shaping evolutionary thinking (the 30th anniversary edition was published in 2006). It was, however, controversial as much for its implications as for the gene centered view it supported. According to Dawkins, the book was misinterpreted and used by some groups as biological justification for selfishness in humans; but his intention was to explain how natural selection works, not how people should behave. Dawkins clearly points this out in the first chapter of the book:

“I am not advocating a morality based on evolution. I am saying how things have evolved. I am not saying how we humans morally ought to behave.”

The Metaphor

The title, The Selfish Gene, is a metaphor for how genes propagate. By controlling the traits of organisms, genes influence their own survival. The genes that aid in survival and reproduction are more likely to be copied in future generations. In that sense the genes are selfish and potentially immortal (in the form of replicas), while the bodies that contain them are mortal. Dawkins writes:

“Individuals are not stable things, they are fleeting. Chromosomes too are shuffled into oblivion, like hands of cards soon after they are dealt. But the cards themselves survive the shuffling. The cards are the genes…They are the replicators and we are their survival machines. When we have served our purpose we are cast aside.

genesThe selfish gene metaphor, though powerful, has its limitations; a single gene can’t do very much. Genes interact with each other and combine in complex ways to give rise to physical traits. It is essentially groups of genes that survive (genes that work well together). Therefore, a successful gene can be defined as a portion of genetic material that survives through a number of successive generations.

 Explaining Altruism

“Survival of the fittest,” that is the popular catchphrase for evolution. But an analysis of the mechanisms of evolution requires that we ask: the fittest what? For Darwin, it was the fittest individual that would survive and reproduce. In the middle of the 21rst century, biologists were reintroducing and debating Darwinian ideas. Group selection (the idea that the fittest groups would survive) was gaining popularity. The propagation of the species was the consequence of the fittest groups. However, some biologists were pointing out that group selection was inadequate to explain altruism in animals.

Altruistic Behavior in  Animals

Dawkins is a zoologist by training, and The Selfish Gene focuses mainly on the role of genes in animal behavior. He analyses animal behavior in a variety of species, and points out the correlation between altruistic behavior and relatedness. In other words, the closer the relationship (in terms of shared genes) the more altruism we can expect to see. In this view the genes are at the core of the altruistic behavior, as they aid in the survival of copies of themselves.

zebrasWhen an animal acts altruistically, it appears that the animal is sacrificing some survival need in order to increase the chance another will survive. It does not matter how small the sacrifice is, because a number of small sacrifices can accumulate over time, and also can be reciprocated. The group selection hypothesis interprets altruism as benefiting the group, and in the long run, these groups will be more successful. However, others claimed that selfish individuals would undermine the altruistic group. The selfish individuals within the group would exploit the altruistic system, eventually winning out. The struggle for existence would favor the selfish individuals over the altruistic individuals.

Dawkins argues that seemingly altruistic behaviors can be interpreted differently from a gene centered view. From the gene point of view, the act is still selfish because it aids exact copies of itself (in the form of children, siblings, cousins and so one). Animals are sometimes altruistic because they are programed by their genes to be so. Whether to be selfish or altruistic is a delicate balancing act that is ultimately guided by the genes chances of survival. In addition to helping close relatives, individuals are also dependent on groups. Therefore some consideration for the well-being of the group would likely come into play.

The Social Insects

Perhaps no other example of altruism in animals is as evident as in social insects. This is probably the best example of which a gene centered view of natural selection is adequate. Honey bees, wasps, ants and termites are familiar social insects, and they live in large colonies. The colony functions as a highly organized unit, where each individual has a specific role. Although the roles vary, they can be broken down into two main categories: Carers and bearers. The carers are sterile workers; the bearers are the reproductive females (queens) and reproductive males (drones or kings).

In most species each individual shares in the caring and bearing roles (not necessarily equally). But with social insects it is clearly divided. The sterile workers will devote their lives to providing and protecting the reproducers, even to the point of suicidal actions. This is what we observe when a bee stings a perceived threat to the hive. The bee will almost certainly die.

With an individual selection view, we would not expect suicidal behavior to evolve, because there is nothing to gain for the individual. However, the fact that the workers cannot bear offspring of their own, self-sacrifice for the good of the colony aids in the survival of their genes (shared genes with the reproductive members of the colony). From the gene centered view, what really matters is not just reproducing offspring, but assisting the survival of one’s own genes. There are many strategies in which this can occur (usually a balance of risk and reward). The triggers for the behaviors are surely subconscious. You could say they are controlled by the genes, or call it instincts.

Are Genes Really in Control?

Although there are mountains of evidence that shows life does evolves, determining the level of selection is tricky; it seems like a matter of interpretation. It is not hard to see how each unit of selection would naturally influence the others in the same way (either positively or negatively). For example, if the fittest individual is selected, it will aid its group, species and genes to propagate. We could change the last sentence by randomly shuffling the units (individual, group, species and genes) and it would still hold true.

Maybe natural selection is a complicated process that includes several units of selection. Species, groups, individuals and genes are likely interconnected in ways that are difficult to quantify. I suspect that this issue is not completely resolved among scientists. Nevertheless, I find that the gene centered view is both fascinating and compelling. It is a somewhat counter-intuitive way of looking at evolution, and yet upon closer examination it makes so much sense. Logically, it all hangs together.

 

References: Richard Dawkins, The Selfish Gene (Oxford: Oxford University Press, 30th anniversary edition, 2006).

Beautiful Minds: Richard Dawkins, Published on April 25, 2012. BBC4 https://www.youtube.com/watch?v=C2I8f4lpBLU


 

The Abundance of Nature

wild flowersIn many respects planet Earth is a rare and unique place. This is partly due to the abundance of nature. There is abundant opportunity, quantity and diversity, as well as abundant time and space. No matter where we look, we will find that things come in large quantities. There is rarely just one of anything in nature; if there is, it probably won’t last for very long.

For our convenience, we separate and categorize the components of nature. Inanimate substances and living things make up two large categories, which are broken down into smaller subgroups. This is useful for us, but in reality the Earth is a living planet. What we consider as inanimate is shared and circulated to maintain all life on earth. For example: soil, water, air and sunlight are part of the living world (in a roundabout way).

Natural Selection and Exponential Growth

Natural selection, Darwin’s term for nature’s sorting process, has a subtle implication; similar patterns and forms are repeated over and over again. This is an unavoidable consequence of natural selection. In order for environmental conditions to serve as a shaping force, it must be favorable for numerous life forms. If only a few individuals are favored, then randomness necessitates that their genes will not be passed on in the long term. On the other hand, when selection acts positively on large numbers (of genes, individuals, groups or species), then the odds are high that they will prosper.

Success from an evolutionary standpoint means survival and replication. There is a constant competition for resources; there are always winners and losers. Once something gains an upper hand, exponential growth will lead to an abundance of that particular life form. It is similar to compound interest in a bank account. Of course, abundance does not entail permanent growth. All species will eventually decline or become extinct due to ever-changing conditions. Nevertheless, when anything survives the process it will do so in large numbers, otherwise it would not be here.

butterfliesFor example, if favorable conditions (such as a plentiful food supply, lack of predators and a temperate climate) are present for a particular species, then the numbers will likely grow. This may at some point lead to overpopulation and stress the survival needs of the species, which can create an opportunity for competing species. The growth of species will usually fluctuate; but most of the time a balance will develop, somewhat like the swinging of a pendulum. In the end the diversity of life will almost ensure that life as a whole will be plentiful.

Self-Organization, Order and Randomness

Both the living and non-living world has the ability to self-organize. That can partially explain how order emerges from a random and chaotic world. The process of self-organization in nature is messy, nothing like we organize our daily lives. With humans there is usually a clear direction or purpose when we make plans. But not all the time; humans also self-organize when groups of people act in a similar way, even if no one is in control.

In nature, the terms trial and error best describes how order and structure arises. There is a role for both order and randomness in this process. The order allows for stability, the random component creates opportunities for change. For example, if we think of how seeds from plants are dispersed, we can see that they fall to the ground in irregular patterns. There is no reason why any seed will come into contact with fertile soil. In fact, the majority of seeds will be wasted. Still, within each seed contains the information necessary to produce the plant. And due to the abundant production of seeds, by random factors alone some seeds will find a prosperous location.

treeFor instance, a mature tree can produce thousands of seeds, and yet, only a tiny fraction of those seeds will become trees. Looking at this process from an individual seed, it seems that the survival chance of a seed is extremely low. But if we account for all the seeds of a tree, there are bound to be seeds that are deposited in just the right location. This is just one example of many similar situations where the abundance of nature assures that life will go on and flourish.

 The Goldilocks Zone

The term Goldilocks Zone is often used to identify the location of the Earth. The idea being that our planet is just the right distance from the sun to support life. The Earth’s location allows for a narrow band of temperature variations (in relation to the universe), a range that can provide liquid water. For water to exist it cannot be too hot or too cold. For life as we know it to exist, liquid water is an absolute must.

At first glance the Earth’s precise location seems highly improbable; however, like the seeds from a tree, there are huge numbers of planets that can’t support life. Hundreds of planets outside our solar system have been discovered, and there are surely countless more. Thus far only a few exoplanets (planets outside our solar system) could be considered as earth like. Out of over 1800 that have already been found, most cannot support life as we know it.

Goldilocks Zones are applicable to situations on earth as well. All life is sustained by a narrow range of conditions. However, because nature allows for abundant opportunity, quantity and diversity something will always find the right location (or conditions). Clearly, from any perspective, there is abundance of every kind. This is what we observe when we examine the natural world. That is why in the grand scheme of things, nature always flourishes.


 

Darwin’s Theory of Evolution: The Best Idea Ever

Charles darwinCharles Darwin’s 1859 publication, On the Origin of Species, changed the way we look at biology forever. Its central idea, evolution by means of natural selection, explains how all life evolves. No single idea has ever explained so much. It stands apart from most, if not all, scientific discoveries in its outreach and simplicity. As with most great ideas, once grasped, one is inclined to ask: “Why didn’t anyone think of this before?”

Actually, others had similar ideas before Darwin, including fellow naturalist  Alfred Russel Wallace. Wallace had figured out that species evolve through natural selection and sent Darwin his version prior to Darwin’s landmark publication. In 1858 they jointly presented their work to the Linnean Society of London. But ultimately, it was Darwin’s detailed explanation in 1859 that history would recognize.

The Idea

Organisms evolve over time by means of natural selection. Each generation is tested by its environment; the traits that aid an organism to survive and reproduce will tend to be passed on to the next generation. Not necessarily all the time, but often enough or in greater numbers. Traits that are not useful will tend to be discarded when the organism that bears them fails to survive or reproduce.

Through this process survivors are copied with slight random variations, which are then tested many times over. In other words, survivors live longer and usually reproduce more, keeping their survival traits alive in the ensuing generations. Darwin wasn’t the first to suggest that organisms evolve from previous forms, but he provided the mechanism (natural selection).

Why is This Idea so Special?

  • Outreach: Natural selection provides an explanation for how all of life evolves. It accounts for microorganisms, plants, fish, insects, birds, animals and of course humans.
  • Simplicity: As oppose to other notable scientific ideas it can easily be understood by the general public. One does not need any technical science background to grasp the basics of this simple, yet elaborate idea.
  • A confidence boost for science: Before Darwin, few could have predicted that all life on earth could be explained by natural means. Ever since Darwin, few should doubt the power of science to explain just about everything else.
  •  Philosophical implications: Darwin compelled us to take a second look at our place in the world. Long-held beliefs that humans held a privileged position, separate from the other creatures, had to be re-evaluated.
Darwin's Tree of Life

Darwin’s Tree of Life

The Controversy

Darwin delayed the publication of his theory of evolution for about 17 years, because he feared a public backlash. And he was right in assuming that controversy would follow. His chief concern, I can only speculate, was probably religious. Natural selection can easily be viewed as taking god out of the creation business. If nature is shaping all of life, what is god left to do? Despite some criticism, his book drew worldwide interest. Even today evolution still gets some people upset. Why is such a profound idea so difficult for some? Let’s look at possible reasons why:

  • Religious : Evolution contradicts the bible’s account of creation; however, many people seem to have no problem squaring evolution with the bible. They either don’t really know what the bible says or they don’t take it literally. Whereas literal interpreters of the bible clearly see what evolution means for their faith. For them evolution is akin to a fatal blow.
  • Supernatural thinking: If one is inclined to believe that there exists a dimension outside the laws of nature, then anything is possible. Life can then be guided by a supernatural force. If that is the case, evolution is no longer required as an explanation.
  • Evolution is confused with natural selection: I suspect that some people think of evolution as simply gradual change over time. In terms of the cause, they can use their imagination. However, the key insight is the means by which change happens. Evolution is the process and natural selection is the mechanism.
  • Deep time: There is nothing in everyday experience that can prepare us for the time scales involved in evolution. Simple life emerged on earth (in the ocean to be exact) 3.8 billion years ago. And from there spread to all regions of the planet. That’s 38 million centuries for life to evolve to eventually create you and me. Given enough time, minor variations in each generation can result in changes that may be hard for some to grasp.          
  • Sometimes the truth hurts: There is no plan in evolution, no final destination that has to be achieved. Furthermore, human beings don’t hold any privileged position in the tree of life. Darwin described life as a family tree, with different species spreading in all directions. Life could no longer be seen as analogues to a ladder, with humans occupying the top rung.  

A Scientific Idea

Darwin’s idea was much more than a moment of insight. It was a scientific idea, a theory that he developed based on years of experience as a naturalist. As a young man Darwin sailed across the globe on the HMS Beagle. He accompanied Captain Robert FitzRoy on a 5 year journey, where Darwin collected a multitude of natural specimens and fossils. It is on this voyage, from 1831 to 1836, that Darwin gathered extensive evidence for his theory of evolution.

Darwin collected many fossils; some were from ancient sea creatures, which he found in mountainous regions. This was clear evidence that mountains moved over time—that a high altitude had once been under water. From a geological perspective the earth had changed slowing throughout the ages. This principle of gradual change over time was extended to include life forms. If the earth changed, life could also change.

Influential to forming his ideas, Darwin collected bird specimens (finches) from the Galapagos Islands in South America. He noticed that the shape of the finch’s beaks varied depending on the island they came from. Darwin reasoned that the finches all originated from a common ancestor, and had evolved different beaks. The finches had become isolated on separate islands, thus evolving differently to meet the demands of the local food supply.

These and other similar ideas got the wheels in motion for Darwin, showing him that species were not stable, that they can change dramatically over long periods of time. Some of the fossils he unearthed were from extinct species, distant ancestors that resembled species that were still living. He also examined different mammal skeletons and noticed they were all variations of a similar bone structure. Beyond his own ideas, Darwin corresponded with other naturalist around the world through letters, thus gathering piles of information.

It would eventually culminate in the publication of On the Origin of Species. Darwin surely struggled with the implications of his theory, as it would have been radical in Victorian England. Creationism was the overwhelming belief of the time; however, it became clear to Darwin that organisms where not created in their present form. Darwin must have been apprehensive upon the publication of his book. Nevertheless, he was guided by the overwhelming evidence he observed as a scientist. He had to accept what his scientific mind was telling him, regardless of the belief of the day. Darwin’s Theory of Evolution is a great scientific idea, and that is why it still stands today.

 

References: The Genius of Charles Darwin, The Science Foundation, https://www.youtube.com/watch?v=ptV9sNezEvk, Published on Jan 12, 2011.