Posts Tagged ‘ Darwin ’

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

Natural Selection


Natural Selection is a simple yet very powerful idea,  the concept that the blind forces of nature can act in place of a purposeful breeder to bring about change in a species leads to some profound conclusions. At the same time it is also one of the most misunderstood and reviled theories in science today.

What is Natural Selection?

Natural Selection is an explanation of the variety of life that we see all around us that is modeled from artificial selection performed by human breeders of animals and crops. One of the most easily grasped examples of this is dog breeders. Over the last several thousand years that canines have been domesticated we have molded them from a few varieties of wolf into the almost dizzying number of breeds we have today. The ancestors of each breed were selected for particular traits that were useful or otherwise desirable to the breeders of the time. The end result was an animal that in some cases bears only a passing resemblance to the original stock.

Wolf vs Bichon Frise

Wolf vs Bichon Frise

American Fantail, Romanian Naked Neck

Bruner Pouter, American Fantail, Romanian Naked Neck Pigeons

Where Natural Selection differs is that it posits that the role of intelligent breeder can be replaced by unintelligent natural forces. In this case the qualities selected for are not matched against some future ideal but what is best suited for the existing environment. In other words the forces influencing evolution can not select for the eventual creation of a particular body plan or anatomical structure, there is no room for foresight in this system, each change must be adaptive in the environment that the organism finds itself.

It is now accepted that whales and dolphins evolved from land dwelling animals, natural selection did not decide to turn them into sea faring creatures and induce the changes necessary, each intermediate step had to suit the animal’s life style at the time and make it better able to compete with it’s rivals.

Whale evolution

Whale evolution; Source: PBS - WGBH Boston "Evolution" Project

The unintelligent natural forces I mentioned above can be climate, terrain or other organisms. In the later case one situation that can result is a sort of “arms race” where a change in one organism influences a change in another which in turn feeds back to the first. Consider a predator/prey relationship. If the prey organism by chance starts down a course of running speed as the means of avoiding becoming dinner then the slower predators will tend to eat less often than their faster compatriots. They will then tend to die more frequently and have fewer offspring. In this way the genes for faster running speed will spread through the population and become dominant in the predators. In turn as the predators get faster the slower prey will succumb to them more often and leave the responsibility of continuing the species to the sprinters among the prey population. And so on. This will presumably continue until some sort of fundamental limit is reached.

There is also an intuitive notion that evolution is a sort of ladder whereby bacteria and other simple organisms are on the bottom and are “primative” with fish coming after them, mammals after fish and Humans at the top reresenting the pinnacle of evolution. Tempting as it is however this is absolute nonsense, there is no steady march toward some idealised perfection in the progression from “simpler” organisms to “advanced” organisms. Each animal or plant or single celled organism is as evolved as any other, each as suited to it’s environment as it needs to be to survive.

Yesterday: Origins                                  Tomorrow: Sexual Selection

Origins


When starting an explanation it is usually best to begin at the beginning to avoid confusion. For evolution this means going back to the first appearance of life on this planet. As is often said, no-one was around at this time so we don’t know exactly what happened but we can make a few hypotheses and test them to see how they stand up.

There are several ways of looking at how life started depending on how you define it. If you define life as an entity that is:

  • separated from it’s environment by a membrane or skin,
  • intakes food to drive metabolic processes that allow for…
  1. the replication of genetic information and
  2. building of supporting molecules and structures for the purposes of creating offspring.

Then you might conclude that the origin of life was a vastly improbable event that could not possibly have taken place without help, then you’d congratulate yourself on discovering the answer to one of sciences greatest mysteries and grab some lunch. Or, you might decide to consider the origin of life to depend on earlier molecules that we would not today consider to be alive but were the necessary precursors that allowed life to arise from non-life, a process known as abiogenesis. Then you go about looking for candidates for such molecules and actually evaluate the evidence.

Scientists consider RNA to be a good candidate for these precursor molecules and refer to the time at which they were the stepping stone to true biology as the RNA world. The attractive qualities of RNA that lead to this hypothesis is that RNA is used in the biological world and so we don’t need to imagine exotic molecules, RNA can catalyze reactions in the same way as proteins so it doesn’t need those supporting structures and it is possible for it to be the template for it’s own replication in the same way as DNA so it is it’s own genetic material.

In this way life could have started out as a single or small number of similar RNA strands that had the ability to replicate themselves and so become more numerous in the environment and “out compete” the existing molecular species that could not replicate. Today ribosomes are in every cell in the world, working to translate the DNA code into the protiens that make up our bodies and perform the chemical reactions that keep us alive. The active components of these ribosomes are made out of RNA and may be a relic that owes it’s existence to the proposed RNA world that could have come before complex life.

Recent research by scientists at the Scripps Research Institute has lent weight to this line of reasoning. They managed to create pairs of RNA enzymes that each catalyze the replication of the other in solution. Variants of these molecules were allowed to compete for the resources available and the more efficient pairs became dominant in the population.

It is tempting to think of this experiment as accurately reflecting how life really arose but it is important to remember that this is more of a “proof of concept” to show that it could happen, not that it did happen just like this. But creating simple chemical evolution in a test tube is exciting. We should also remember the the theory of evolution by natural selection proper concerns only what happens once life is on the scene and has little to say on how it actually got started but it is a question that is very much related and one that is being worked on.

Yesterday: Intro                              Tomorrow: Natural Selection.

12 Days of Darwin


Introducing the 12 days of Darwin, this year sees both the 200 anniversary of Darwin’s birth (12 Feb) and the 150 year anniversary of his publication of ‘On the Origin of Species by means of Natural Selection’ (24 Nov). As such I thought it was worth devoting a series of daily posts centered around evolution in the days leading up to Darwin Day. These posts will constitute everything you never wanted to know about evolution and more. From the origin of life to fossils, molecular genetics to the Cambrian “explosion” I will be covering as many different aspects as I can. The plan is for a post a day up until the 12th so we’ll see how that goes, my penchant for procrastination may get the better of me.

Darwin Day celebrates the birthday of Charles Darwin and has become a starting point for educating the public about evolution and initiating a dialogue with the community. Since Darwin death in 1882 celebrations of his contribution to science have been sporadic, only in the later part of the 20th century has there been an effort to organize and start ongoing traditions. This is probably a response to a perceived increase in public pressure against evolution education, especially in the United States.

To start out the 12 days of Darwin here is a summary of the events happening in New Zealand and Australia so you can get a feel for what’s going on.

Events in New Zealand:

The Charles Darwin Theater Project
Starting at the Te Papa museum in Wellington before going on tour this consists of a play about Darwin and will run along side public debates and lectures organised by the Royal Society of New Zealand.
http://www.darwinday.org/events/listing.php?id=12425

Darwin’s 200th Birthday Symposium
The University of Auckland’s Bioinformatics Institute and the School of Biological Sciences will hold a free one-day symposium that brings together leading national and international thinkers who will speak of the impact of Darwin on their research in biology, medicine, history and literature. This event has been designed to appeal to a general audience.
http://www.darwinday.org/events/listing.php?id=12504
http://www.darwin.org.nz/

[Update]
Allan Wilson Centre Lecture Series
Every two years the AWC hosts a series of three lectures focusing on a theme of interest. In recogntion of the 200th birthday of Charles Darwin and the 150th anniversary of his publication “On the Origin of Species” the theme for the 2009 series is “Human Evolution”.
http://www.allanwilsoncentre.ac.nz/outreach/lectures.htm

Events in Australia:

Evolution – The Picnic
Celebrate the 200th birthday of Charles Darwin with a picnic at the Mornington Park. Event put on by a Philosophy Cafe and Skeptics Group, known as the Free Range Brains.
a Philosophy Cafe and Skeptics Group, known as the Free Range Brains. http://www.darwinday.org/events/listing.php?id=12492
http://www.meetup.com/Teapot-Mornington-Peninsula/calendar/9596118/

Evolution: the Experience
International Conference exploring the depth and breadth of Darwin’s impact on science and society.
Evolution: the Experience International Conference exploring the depth and breadth of Darwin’s impact on science and society. http://www.darwinday.org/events/listing.php?id=12527
http://www.evolution09.com.au/

Darwin Day Barbecue
Celebrate Charles Darwin’s 200th birthday at the Yarra bank BBQ near the Morell Bridge.
http://www.darwinday.org/events/listing.php?id=12550
http://home.vicnet.net.au/~atheist/DarwinDay_BBQ.htm

Charles Darwin Dinner
A special dinner at Gardners Inn in Blackheath NSW Australia to celebrate the time in 1836 that Charles Darwin stayed at Andrew Gardners Inn in the Blue Mountains.
http://www.darwinday.org/events/listing.php?id=12581

Darwin Day: Art, Beauty, and Evolution
A public tribute and lecture by Professor Denis Dutton, founder and editor of acclaimed website Arts & Letters Daily.
http://www.darwinday.org/events/listing.php?id=12603
http://www.cis.org.au/events/darwin_day.html

Darwin Day Celebration
Film night to watch Randy Olson’s film wonderful docudrama ‘Flock of Dodos – the evolution – intelligent design circus’.
http://www.darwinday.org/events/listing.php?id=12610

AND More….
See http://www.darwinday.org/events/listing.php for full up-to-date listings.

Tomorrow: Origins

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