Posts Tagged ‘ evolution ’

Intelligent Design Flaws: The Evidence for Natural Selection in Our DNA


Here in New Zealand the debate between religion and evolution is a muted affair, while news on the topic regularly makes headlines in the US, here it goes almost beneath notice. That is not to say the clash does not exist here, merely that it tends not to intrude into the public sphere. Over time the form of the argument has changed but at its heart the source of the conflict has remained the same, discoveries in science have unseated the traditional view of a divinely created world in which Humans are the pinnacle of creation.

At this point I would like to make it clear that the findings of science are not incompatible with such a view.  Even so, to accommodate the conclusions of scientific enquiries into nature certain tenets that were previously held to be literal truths (such as 7 day creation) must be reinterpreted symbolically. As in any human endeavour there exists a spectrum of approaches to the religious significance of science’s discoveries. To some, science represents the deepest truth we can know about the world, provisional as it may be, and as such must also inform the religious outlook. For others revealed scripture is the ultimate authority and where this disagrees with science, well, so much the worse for science. Most people fall somewhere between these two extremes.

I seldom wade directly into this debate but recently came across a paper that outlines some of the peculiarities to be found in our genome (in particular but multicellular life in general) which was framed in the context of refuting design. The paper is “Footprints of Nonsentient Design Inside the Human Genome” written by John C. Avise and published in Proceedings of the National Academy of Sciences. Before getting to the crux of his argument Avise spends some time to give a brief history of three concepts that have a bearing on the discussion of design in nature. Touching on Socrates, Reverend William Paley’s famous work “Natural Theology” and Darwin’s own thoughts on the topic Avise gives a primer on how the natural world was considered in pre-Darwin times. From here we move onto the rise of modern Creationism and Intelligent Design, charting it’s progression from the early 1980s to the more recent strategy of proposing the concept of “Irreducible Complexity“.

Finally there is a similarly brief sketch of Theodicy, or the attempt to reconcile the existence suffering in the world with the traditional view of an all-powerful and all-loving deity (if you are playing charades I recommend doing “sounds like” and then try acting out Odysseus’ journey following the fall of Troy). This last seems somewhat out of place in a paper such as this but the relevance becomes clear once the author begins to expound on the multitude of human ailments that are the result of imperfections in the architecture and the replicating processes of our genome.

The numbers involved and breadth of disease in this section are truly staggering, to quote from the paper itself:

Various mutations are known to debilitate the nervous system, liver, pancreas, bones, eyes, ears, skin, urinary and reproductive tracts, endocrine system, blood and other features of the circulatory system, muscles, joints, dentition, immune system, digestive tract, limbs, lungs, and almost any other body part you can name.

In covering the various methods we use to keep track of genetic diseases, one of which being the reference text “Mendelian Inheritance in Man” Avise notes that “the current version of which describes thousands of human genes, of which more than 75% are documented to carry mutational defects associated with a disease condition.” and concerning another effort at documentation the “Human Genome Mutation Database” states “recent versions of which describe more than 75,000 different disease-causing mutations identified to date“.

After all of this preamble we finally get to the design flaws we have been promised, the first being “Split Genes”. Here is where things get technical. A quick “Genetics 101″, while we may think of genes as being discrete entities in our cells that code for the proteins making up our bodies, one gene to one protein, things are actually a lot more complicated. What actually occurs for many genes is a long stretch of DNA, some of which is needed for the gene and some of which isn’t. These parts are called Exons (needed bits) and Introns (extra bits), imagine reading Harry Potter and finding someone had randomly glued in pages from the dictionary. This means each time our cells want to make a new copy of a protein the extra bits need to be chopped out and the needed bits stitched back together first.

This process is both wasteful (unnecessary copying and fixing of the gene coding regions) and harmful, to quote once again:

“An astonishing discovery is that a large fraction (perhaps one-third) of all known human genetic disorders is attributable in at least some clinical cases to mutational blunders in how premRNA molecules are processed”

Next up is is a section discussing gene regulation and surveillance of errors. I have to say, this part is too complicated for me to parse ant this late hour. So I’ll leave that one for the adventuresome. Suffice it to say that the regulation (turning genes on and off) and copying of our genes is a complicated and error prone business, too much so if we are to consider it the perfect solution to the problem of creating human life.

The next stop on our curious ride is the mitochondria, or more specifically mitochondrial DNA. You may recall the oft repeated refrain that the mitochondria is the “powerhouse of the cell”, not to be confused with midichlorians which mediate the power of the Force. The mitochondria contain the reactions that allow us to extract energy from our food, without them you would die in very short order. It is one of the more intriguing facts about our cells that the mitochondria are equipped with their own DNA, and yet this DNA does not contain all of the information required to carry out the life giving energy reactions, it is supplemented by the DNA contained in the nucleus of the cell, your genomic DNA. Not only this but the interior of the mitochondria is a poor place to keep DNA, it is after all where energetic reactions are being carried out and toxic waste products are produced. Would you keep a valuable library in a working furnace?

These facts are all but inexplicable (and a great many more are mentioned in the paper) by appeal to a perfect designer but they are relatively easily dealt with via the paradigm that mitochondria are the remnants of a symbiotic bacteria. One which long ago insinuated itself into our cells and over the millennia has shed much of it’s own genome while housed in it’s comfortable new habitat. An analogy might be the loss of certain mathematical abilities in modern students who rely on electronic devices to to the hard work of calculation for them.

The paper goes on to deal with repeating sections of DNA, the existence of duplicated genes and pseudogenes and roving DNA that copies itself around the genome. But you can read about those for yourself, this post is already more than typically verbose. I would just like to sum up with the final hopeful run-on sentence (cousins of which plague my own writing) of the author:

“The evolutionary-genetic sciences thus can help religions to escape from the profound conundrums of ID, and thereby return religion to its rightful realm—not as the secular interpreter of the biological minutiae of our physical existence but, rather, as a respectable philosophical counselor on grander matters, including ethics and morality, the soul, spiritualness, sacredness, and other such matters that have always been of ultimate concern to humanity.”

Not exactly an uncontroversial sentiment itself.

Avise, J. (2010). Colloquium Paper: Footprints of nonsentient design inside the human genome Proceedings of the National Academy of Sciences, 107 (Supplement_2), 8969-8976 DOI: 10.1073/pnas.0914609107

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Intelligence, Monogamy and Journalistic Licence


ResearchBlogging.org
Last week news came out about a study linking intelligence with liberal attitudes and atheistic beliefs, oh and in men an increased tendency for monogamy. Today I read the NZ Herald‘s short take on the study, a semi-chauvinistic piece pointing out how we evolved intelligent men can think our way to monogamy while those sexually immoral women can’t. I felt just a little dirty reading it. Ok, perhaps it isn’t really that bad but having being familiar with the study before reading the story that’s how it stuck me.

The full published study is locked behind Social Psychology Quarterly’s pay wall but the lead author, evolutionary psychologist Satoshi Kanazawa, rather nicely provides copies of his papers on his own website. I like him already. The paper, rather provocatively called “Why Liberals and Atheists Are More Intelligent.”, discusses a concept Kanazawa calls the Savanna-IQ Interaction Hypothesis. Essentially this states that our behaviours were shaped by our evolutionary past and that intelligence may allow us to adapt these behaviours and introduce new behaviours that are “evolutionarily novel”. In this scenario general intelligence (IQ) evolved as a mechanism by which we could adapt to novel situations that our genes alone had not equipped us to deal with.

To investigate this principle three types of evolutionarily novel behaviours/values were examined to determine if there was any correlation with intelligence. To wit the behaviours looked at were liberalism, atheism and monogamy. Throughout the paper the relation of monogamy to men as being evolutionarily novel specifically excludes women, not because women’s behaviour in this regard cannot be moderated by intelligence but because monogamy is not a novel concept for women. In our evolutionary past women (according to the hypothesis) would always have been more monogamous and so this would be classed as an evolutionarily familiar strategy which does not require higher intelligence to change thus the prediction that intelligence would not be correlated with greater monogamy in women where it would be in men.

In fact multiple studies have already shown that across cultures women tend to be more monogamous so what this study implies is that men have to be more intelligent (in order to overcome our stupid genes) just to get on a par with women. Frankly though this is the least interesting part of the study. More fascinating (though also more potentially inflammatory) is the association of intelligence with liberal and atheistic modes of thought. For the purposes of the study Kanazawa simplified the definition of liberalism to:

“the genuine concern for the welfare of genetically unrelated others and the willingness to contribute larger proportions of private resources for the welfare of such others.”

Stated in this way the concept actually looks a little unfamiliar to me as well as my hypothetical ancestor. But if I consider it for a while I can squint my eyes and see it as encompassing most of those values I generally lump together as being liberal. In any case Kanazawa’s argument boils down to the conjecture that our ancestors would not have lived in societies in which we would have been surrounded by large numbers of unrelated individuals such as we are now. In this case they would not have had much incentive to develop behaviours which valued unrelated strangers as much as ourselves, in fact I could see this sort of behaviour as actually being detrimental.

This may explain why liberal people are more intelligent than their conservative counterparts but it does not address the question as to why intelligence might lead to the adoption of these principles, why aren’t we just more intelligent conservatives? What’s so great about being liberal?

The question might be slightly clearer in the case of atheistic beliefs as those that espouse this point of view tend to make it into an argument about truth. Certainly there must be an advantage to knowing the truth about the world around us but how this might relate to a more or less abstract truth such as the existence or absence of a deity is not obvious. I would be interested to see if intelligence is more highly correlated with believing more concrete truths about the world independent of actual scientific training (which presupposes that the beliefs formed about the world in this fashion are approaching trueness).

Fun as these topics maybe to speculate about it’s difficult to say how much these sorts of studies tell us about the evolutionary origins of particular behaviours as I have seen in comments to this study elsewhere it smacks of just so stories. I’m not an evolutionary psychologist so I’d rather stay away from interpretation in this vein but perhaps we would do well to take any conclusions with a grain of salt, especially if those conclusions are what we want to hear.

Reference:
Kanazawa, S. (2010). Why Liberals and Atheists Are More Intelligent Social Psychology Quarterly DOI: 10.1177/0190272510361602

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Evolution – The Story of Life


I was sitting at my computer this morning wondering if I would suddenly be inspired with a topic to write about or whether I would resort to my default setting of abject sloth. Then inspiration did strike, in a way, my copy of “Evolution – The Story of Life” arrived by courier. Written by Douglas Palmer and illustrated by Peter Barrett this is a fantastic large format hardcover book that takes you on a trip through the history of life on planet Earth. From the appearance of single celled organisms, through the proliferation of forms during the Cambrian period and finishing up with the life we see around us today.

Evo

Beginning with introductory information explaining what evolution is as well as briefly covering the history of the theory, the time scales involved, taxonomy, fossils and how it all comes together this book will be accessible reading for anyone.

The book is beautifully illustrated throughout, touching upon each major stepping stone from the beginning to the present day. Every turn of the page brings a new vista with examples of flora and fauna typical of each age and location depicted. Below the impressive artwork is a brief description of the area and life shown as well as an information box showing a representation of the distribution of the continents at the time compared with how the particular location is situated today. Rounding out the informative package are photographs of actual fossils from the period.

Info Box

I was particularly taken with the Cladograms that show how the species of animals are related. The major levels of the tree of life each have their own cladograms; Metazoa, Tetrapoda, Mammalia and certainly not forgetting Primates.  These fantastic illustrations provide a great overview of the interrelatedness of species and are a fascinating read.

CladeFinally the book ends with a “Species listing”, an A-Z of the species depicted in the book featuring pictures of plants, animals and fossils. Each entry gives the time period the life form lived, it’s place within the tree of life, a brief description and the reference to were it can be found in the earlier pages of the book.

At the back of the book can be found a condensed timeline of the geological and evolutionary history of our planet. In addition all of the artwork in the book is reproduced side by side to show a continuous panoramic view of the story of life.

Evolution The Story of lifeI think I say without too much exaggeration that this book is truly a masterpiece and a great addition to any collection. Highly recommended.

Evolution Survey


Just a quick post to spread the word about a survey covering the public acceptance of evolution in New Zealand and the effect (if any) of religious/spiritual beliefs on the the extent to which evolution is accepted in the wider community. The survey can be found Here, and the results will be presented around November 2009.

The survey is being conducted by Drs Marc Wilson and Peter Ritchie of Victoria University in Wellington. I hope to secure an interview with the two Drs closer to the release of the data to get their views on the implication of the findings. In the mean time go participate in the survey, it will only take a few minutes and will be time well spent.

Whistling a “Fine-tune”


It is often asserted that the Universe is “Fine-tuned” for life, that if this or that constant was altered even a little bit the Universe would have been completely lifeless. Now the arguments for and against this particular argument are many and varied, I personally don’t see the Universe as being particularly hospitable to life. I mean our proclaiming that everything is just right for our existence and isn’t that amazing is like a flea looking at the dog flesh all around him and saying the Universe is perfect for fleas. The same as the flea we are restricted to a small part of the surface of the Earth, if we venture further out it is almost like the Universe is actively trying to kill us. Most other places have drawbacks of wild extremes from the crushing pressure and gravity of gas giants to the asphyxiating vacuum of interstellar space. Everywhere we look there is either killing cold or killing heat, cosmic rays, tearing gravity or no gravity. So maybe the Universe isn’t perfect for us after all.

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Thermodynamics Vs Evolution: The Grudge Match


The law that entropy always increases holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell’s equations — then so much the worse for Maxwell’s equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.” — Sir Arthur Stanley Eddington, The Nature of the Physical World (1927)

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Darwin Day


“Man with all his noble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men but to the humblest living creature, with his god-like intellect which has penetrated into the movements and constitution of the solar system—with all these exalted powers—Man still bears in his bodily frame the indelible stamp of his lowly origin.”
The Descent of Man, 1871

I was doing so well, you think it would be simple just daily posts for 12 days. Then I drop the ball on the last day and the only one that really mattered. Oh well, it’s still the twelfth somewhere. For this last post in the series I just wanted to briefly look at the writings of Darwin and say you should read them. So far I have not read anything of Darwin’s but I plan to remedy that just as soon as I finish the current book on my list, Daniel Dennett‘s “Breaking the Spell: Religion as a natural phenomenon” which is not a bad read itself. But anyway, in addition to his most famous works “On the Origin of Species” and “The Descent of Man” Darwin also wrote a number of books on a range of topics. Coral reefs, geology, carnivorous plants, worms, volcanic islands as well as a narrative of his time on the “Beagle” and an autobiography are all products of of his pen. Numerous letters have also been collected and published that detail his social contacts and the development of his thinking over time. The website The complete work of Charles Darwin online has a dizzying number of documents boasting 20000 of Darwin’s private papers.

Here’s a quote about Darwins theory:
“[When the theory of creation by evolution] was
first advanced it was met by a storm of dogmatic abuse.
It was ridiculed, pooh-poohed, abused, called the
‘dirt theory,’ and scarcely given a hearing.
Now the tables are completely turned, so that the man who
today opposes it is treated very much the same way as if he
denied the revolution of the earth around the sun.”
These words, rather than being written recently, appeared in the publication “Catholic World”, February, 1882 which contained an article, Evolution, by W.R. Thompson. (reference thanks to The “Popular Press” Responds to Charles Darwin, The Origin of Species and His Other Works Sidney Horenstein published in Evolution: Education and Outreach)

On a geekier note, the Perth Mint has a Darwin Commemorative coin to celebrate the 200 years since Darwin’s birth. Made of 1 ounce of 99.9% pure silver it’s the must have item this year. Be the first Geek on your block to get one. Mine of course arrived several days ago.

Look, it's even in colour!
Look, it’s even in colour!

So, follow my example and read “The Origin of Species” and get a coin to remember your experience by.

Creationists


Quick extra note, Dr. Steven Novella of the Nerurologica blog today posted a great introduction to Creationist arguments and briefly covers the “Cambrian Explosion”, I recommend you pop over there and read this interesting treatise.

Evolution Everywhere


Today I’ve decided to send you away again.

First up is one of the magazine specials that we’ll likely see dozens of this year that centre on Darwin and evolution. It’s from BBC’s Focus magazine and covers topics such as whether humans are still evolving, What Darwin didn’t know, Evolution in action and how to argue with a creationist.

So Check that out, looks like an entertaining read.

Second up is a series of videos featuring one of the greatest popularizers of evolution since Darin himself (Origin of Species was a “best seller“). As well as one of the most controversial and inflammatory, Richard Dawkins. Whatever you think of this now public figure any discussion featuring him is instantly more interesting and his descriptions of evolution are carefully tuned to be understandable by a wide audience without spiraling into condescension. Produced for the National Geographic channel each video is high quality and only a few minutes long. Topic covered in the videos are the importance of Darwin, Fossils & Darwin, Why Darwin Was Right, Creationism then Dawkins’ views on God & the Universe that while in my opinion not strictly relevant to the scientific endeavour of evolution still is one of the first things that many people leap to when considering these ideas.

Again, head over there and consider yourself edified.

Yesterday: Evolutionary “Gems”

Evolutionary “Gems”


As a follow up to yesterday’s post on Transitional Fossils I thought I would highlight another resource put together by the journal “Nature” that brings together 15 short easily read articles on evolutionary evidences along with references and additional resources. Given the name “15 Evolutionary Gems” they have set the stage to showcase some insteresting and foundational topics and they do indeed deliver. A rundown of the contents is as tantalising as I would expect from such a document as you can see below:

Gems from the fossil record
1 Land-living ancestors of whales
2 From water to land
3 The origin of feathers
4 The evolutionary history of teeth
5 The origin of the vertebrate skeleton
Gems from habitats
6 Natural selection in speciation
7 Natural selection in lizards
8 A case of co-evolution
9 Differential dispersal in wild birds
10 Selective survival in wild guppies
11 Evolutionary history matters
Gems from molecular processes
12 Darwin’s Galapagos finches
13 Microevolution meets macroevolution
14 Toxin resistance in snakes and clams
15 Variation versus stability

So from the transition of animals from water to land to the evolution of feathers, the basis of new species to the introduction of sudden changes in animal body plans and everything in between they have it covered. Whether you are just interested in a quick read of a springboard to in depth study this is a great resource. Each topic is covered in less than a single page with usually only two to three paragraphs of text. As such it is a very easy read and certainly does not bludgeon you with overly technical language.

Give it a try, I think you’ll be pleasently surprised.

darwin

Yesterday: Transitional Fossils    Tomorrow: Evolution Everywhere

Transitional Fossils


First lets discuss what fossils are, this is probably redundant but I’ve got to fill my word count somehow. You likely already know the postage stamp version of this, fossils are the mineralized remains of dead animals, but how are they formed and why are there so few of them? Actually the answers to those to questions are the same, the way fossils are formed leads to the natural paucity of the fossil record that those who would dispute evolution decry. Fossils require very particular circumstances in order to be created, the remains of the animal or plant need to be buried quickly in fine sediment such as clay, silt or sand. If the animal is buried fast enough then this may stop scavengers as well as exclude oxygen from the remains and so reduce decomposition. In this case we may get a cast of the exterior features of the animal.

The ever popular Trilobite

The ever popular Trilobite

Once the bones are under a good amount of sediment then the process of fossilization can commence. It’s not a quick process by any means and can happen in several ways. Crystals may develop in the original structure and eventually replace it with a crystallized copy, or the  remains may rot away leaving a hollow that is subsequently filled with rock creating a cast of the original or finally the organic material may be slowly replaced with minerals from the surrounding rock. As I said this process requires that the remains be cover relatively quickly after death and so most fossilization occurs near water where sediments can be washed over the body in a fairly short time. Death inland is usually swiftly followed by the carcass being either torn apart by scavengers, broken and scattered to the wind or decomposition.

Now that we have our fossils what do they tell us? Well the fossil record is a remarkably complete (considering it’s limitations) archive of the gradual change of organisms of the eons for one form to another. The phrase Transitional Fossil is something of a misnomer and gives the wrong impression. As evolution is occurring all the time (visibly or not) every species can be viewed as transitional, including those that survive today. Or to put it another way species can only be viewed as transitional with hind sight and the knowledge that one species preceded another and that was followed by a third. Each species was/is evolved for the environment it live(d)s in and it is only our passion for putting things in order and telling a story that makes it seem natural for us to indulge in the conceit of calling one or another species “transitional”.

Having said that I shall now disregard my own rant and say what are examples of transitional fossils? We one lineage that is now particularly understood is that of horses.There is a list of about 23 intermediate species identified ranging from something like a rodent to deerlike animals and into the modern horse now so familiar. The sequence was first sketched out in the 1800′s and so is now very well understood.

Hyracotherium

Hyracotherium, early horse ancestor

Below is a graphic representation of horse evolution that is quite remarkable and yet does not do the knowledge we have gained justice, as neither does this humble post. But hopefully you will be inspired to look into these examples for yourself.

Horse evolutionary line

Horse Evolution in living colour

Yesterday: Evolution Journal Tomorrow: Evolutionary “Gems”

Evolution Journal


It’s been pretty full on the last few days so I thought I’d take a break and tell you to go check out the (currently) free journal Evolution: Education and Outreach. The first issue of 2009 has just been published and there’s bound to be something of interest for everyone. Actually I especially recommend looking up last year’s fourth issue all about the evolution of eyes and in particular an article written by Dr. Steven Novella on the suboptimal design of the eye, ever popular example of perfection. So browse through it all, the journal has many interesting book reviews, opinion articles and news items. In case you haven’t figured it out yet I highly recommend this journal and think the free period until the end of 2009 should be taken advantage of by everyone who has an interest in science and evolution and everyone else too. Go, go now.

Yesterday: Molecular Evidence Tomorrow: Transitional Fossils

Gene Eye View


The gene centered view of evolutionary change is a useful way to visualize how the processes work and to come up with explanations of why things happen the way they do. I have already mentioned concepts like genetic fitness, genetic lines and goals of an individual and this is where those concepts are grounded. This way of considering things was not originally put forward by Richard Dawkins but he certainly popularized it in 1976 with his book The Selfish Gene.

Gene

Gene

The usefulness of this method becomes apparent when you consider that we are use to thinking of species as individuals, discrete in time and space that act upon the world and are in turn themselves acted upon. But evolution doesn’t happen on the scale of individuals, a particular animal does not evolve the population does, and what produces this change in population characteristics? alterations in the genes. If we reverse our point of view and consider the genes as the primary actors in the evolution games things start to make more sense.

Genes are the true replicators in biological systems, while we may consider reproduction to be about continuing the legacy of an individual into the future in actuality it is the genes that are really being propagated. In addition it is the genes that change over time, not individuals even though in conversation it is useful short hand to refer to, say rabbits, evolving over eons it is really the genes and gene frequencies in the population that we are  discussing.

Given that it is the genes that evolution is really concerned with we can start to put into context the concepts that we have been talking about up until now. In other words when we talk about behaviours or physical characteristics benefiting an individual what we mean is that it helps the individual’s genes survive and replicate and eventually spread through the species. More specifically the gene for that trait is selected by the environment of the individual to continue into the next generation.

In this way when a mutation alters the expression characteristics of a gene (eg making brown eyes blue for instance) it introduces variation in the population of genes and this new variant must compete against the other versions (alleles) in order to continue to exist (be passed on to the next generation). So when we consider how an adaption aids an individual we also need to think in terms of what activity is best for the genes because that is what will be maximized and optimized by nature, that’s just the way it works.

Raphael from TMNT

Raphael from TMNT

Yesterday: Kin Selection Tomorrow: Molecular Evidence

Kin Selection


Do you spend time with your family? Good. Because a man that doesn’t spend time with his family can never be a real man.
-Don Corleone (The Godfather)

It’s all about family, kin selection is the explanation given for behavior that decreases the ability of an individual to have offspring while increasing that of the individual’s family. The most extreme examples of this is found in eusocial insect species such as ants and bees where entire segments of the population give up their “reproductive rights” in order to tend to those who do the reproducing for them.

Of course the ants don’t get together and decide who gets to breed and who doesn’t, that decision is made by the interaction between their genes and the environment they are exposed to. The point is those genes can be selected for under the right circumstances. In species like bees where the colony is mostly composed of the progeny of a single queen the population are essentially all siblings each sharing a significant amount of their genome. In this case they are more closely related to each other than they would be to their own offspring whom would only share 50% of their genes. From the point of view of continuing the genetic line therefore their efforts are better spent raising more siblings than going off on their own to have children outside the colony.

For other animals the genetic payoff isn’t as high but the same principles still apply, why do some animals invest time helping to rear the young of brothers and sisters or children? Because it serves their genetic interests to do so. There is an hypothesis that male homosexuality in humans is this sort of kin selection trait. There is evidence that the genes that confer homosexuality on males increase fertility when they are in a female host, and having homosexual relatives may (there isn’t much evidence for this) increase the pool of helpers mothers can draw on to raise their young. Speculative but fascinating.

So in light of kin selection it becomes less mysterious to explain concepts like altruism, fundamentally altruism means performing actions that benefit another individual at a cost to yourself. If in the environment your genes evolved the individuals you are most likely to meet are your own family members then it is not really a cost to your genetic line to help them. So it makes sense that even though the human population of the Earth has reached the point were you are much more likely to interact with complete strangers on a day to day basis we embody behaviours that compel us to act compassionately towards those around us, that’s the way we evolved and I wouldn’t have it any other way. (Of course I would say that, I’m programmed to)

orangatan

Yesterday: Sexual Selection Tomorrow: Gene Eye View

Sexual selection


As we saw in the entry on Natural Selection the environment of an organism can include other species. It also includes other individuals in the organism’s own species, this is where the concepts of sexual and kin selection can fit in.

Put simply Sexual selection is about ladies choice, in many species the males compete for mates but it is the ladies who have the pick of the winners. In nature there are examples of extreme behavior, ostentatious displays an over developed physical attributes, as there are no free lunches in the natural world what pays for these? The answer has been posited that they increase reproductive fitness not directly by allowing faster running, better hunting or other obvious means but but making the individual more attractive to mates. In fact these characteristics might even become harmful by making the individual an easier target for predators.

Ideally the characteristic signals genetic fitness which is expressed by immunity to disease and parasites and ability to acquire food and avoid predators. Bright plumage would be metabolically costly and make predator avoidance more difficult so only a healthy individual can afford the up keep, one that is susceptible to illness would have difficulty and so show that it was inferior. It may be that some sexual selection is a chance preference in females that spirals out of control. If a female happens to prefer longer than average tails in her mates then those males who have long tails will mate and pass on those genes but, significantly, the female will also pass on the preference for long tails. In this way a trait can rapidly change in a population. It may then become a cost to the male that only healthy males can afford and so becomes a de facto indicator of reproductive fitness. In other words the female did not  choose the characteristic because it indicated a healthy mate.

Long-Tailed Widow bird

Long-Tailed Widow bird

In birds this process can be seen to be taken to ridiculous extremes as the aptly named Long-Tailed Widow bird clearly shows. But there is an interesting hypothesis that the human brain itself is a sexually selected characteristic. Instead of developing “higher” intelligence in response to a changing environment or as a survival trait our capacious craniums may have simply made us sexier. It was our ability to shoot off a witty one liner that was the real target of selection and our increased problem solving just came along for the ride. While this may seem far fetched experiments with fruit flies suggests that under normal circumstances greater intelligence is more trouble than it’s worth this combined with the observation that human like intelligence is not replicated in other species, even among our close relatives, means an explanation like this might be closer to the truth than we’d care to admit.

Yesterday: Natural Selection Tomorrow: Kin Selection

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