Darwin and death

By Martín Bonfil Olivera
Published in Milenio Diario, June 10, 2009

The game of linking concepts that at a first glance look unrelated can be a good way of keeping one's mind in shape. I was invitated to give a talk about "the death of Darwinism", and that's a good excuse to explore the relations between the life and work of Charles Darwin and the subject of death (since Darwinism is alive and evolving).

Darwin's encounters with death are not few. His mother died in 1817, when he was only eight years old; that forced him to be admitted in a boarding school. Years later, already married to Emma, his cousin and then wife, he had ten children, of which two died very young (not an unsual thing in those times). But the death of his favorite, little Annie, at the age of ten, was no doubt the most traumatic encounter of Darwin with death. So much that it is believed that this put an end to whatever rest of religious faith he had left.

Darwin's own death was not unusual: he was buried in with honors at Westminster Abbey, the place reserved for the great men of England. The excessively austere grave on the floor that marks his resting place contrasts with the nearby grave of Isaac Newton, a kind of mini-Disneyland.

Darwin's ideas are too related to death: they help us to understand, for example, how it emerges.

It turns out that the oldest organisms, composed of only one cell, are immortal. They feed, grow and, when the time is right, they divide in two, but they don't die. Only with the emergence of multi-cellular organisms and sexual reproduction do phenomena like ageing and death emerge; they are the price we have to pay for the capacity of forming more complex organisms.

Apart from helping us to understand death, if Darwin's ideas are used in the wrong way, they can cause death: at the beginning of the 20th century, the development of the pseudoscience of eugenics, which intended to improve human race through Darwinian selection, was a global trend, and gave way to the excesses of Nazism. Even today, the application of Darwinian thinking in social contexts bears this stigma.

The moral of the story is that Darwinism, as any other knowledge, can be used for good or bad. That's why it is convenient to have a good understanding of it.

(translated by Adrián Robles Benavides)

To receive Science for pleasure weekly
in your email, subscribe here!

The paradox of species

by Martín Bonfil Olivera
Published on Milenio Diario, April 8, 2009

The human brain tends to simplify. We like to understand things in terms of black and white, good or bad… And we also like to think that things can be defined with clarity: that they have an essence.

A problem when understanding Darwin's theory is the definition of biological species. Although Darwin himself avoided defining it ("…I look at the term species as one arbitrarily given, for the sake of convenience, to a set of individuals closely resembling each other, and that ...does not essentially differ from the term variety"', he wrote in The origin…), he didn't deny the existence of species. Nobody confuses dogs with horses, after all.

The usual criteria to define a species is "reproductive isolation": if two animals or plants cannot mate, or they produce sterile descendants, they belong to different species. But if, however, no matter how different they look, they can mate (like dog breeds), they belong to the same species.

But the reproductive criteria is not infallible (there are canine breeds that don't mate just due to reasons of size), and does not always apply: there are many asexual organisms; bacteria, for instance. Besides, as mentioned here in last week's post a lot of these organisms exchange genes "laterally" (not from parents to progeny, but by a mechanism similar to a "contagion"), so even a more modern criterion, such as gene analysis, does not always allow a clear distinction among species.

On the other hand, saying that "species evolve" is confusing: if a species changes, it turns into another one. So, do species change, or do they just disappear to leave room to other species?

The problem, philosopher Daniel Dennett explains in his revealing book Darwin's dangerous idea, is that what characterizes a species is not the presence of a certain essence that defines it, but the absence of the intermediate forms between one species and the other.

Species are not collections of identical organisms: they are more like clouds of individuals with almost identical genomes, but with little variations. We say that there are two distinct species when between two of these genome clouds there is an empty space; in the opposite case, we talk of varieties. As always, in science things are not as simple they are said to be.

(translated by Adrián Robles Benavides)

To receive Science for pleasure weekly
in your email, subscribe here!

Darwin's little tree

by Martín Bonfil Olivera
Published in Milenio Diario, April 1, 2009

In 1837, returning from his five-year travel on board of theHMS Beagle, and starting the two decades he would spend thinking about the "transmutation of species", Charles Darwin wrote in his notebook the phrase "I think", and then he drew a little branched outline: the first evolutionary tree.

In 1859 he published The origin of species, and the only illustration he included was a more elaborate tree. Since then, the tree is evolution's dominant metaphor: a ramified process in which new species appear from pre-existent ones.

But attacking Darwin is a hobby few can resist, from fanatics that try to banish it to restless biologists that pretend to jump into fame by proving that some of his ideas are wrong.

And of course, there are a lot of aspects in which Darwin was wrong (his theory of heredity, for example, was way out of line). With time, the Darwinian theory of evolution by natural selection has been corrected, completed and fine tuned. Still, it remains as the backbone of modern evolutionary thinking.

Recently, New Scientist magazine published an article that caused an upstir, because it declared that the discovery of "horizontal gene transfer" (not from parents to descendants, but like that which occurs when two bacteria exchange antibiotic resistance genes, or when a virus injects genes from another species into us, as has happened lots of times in human evolution) is the downfall of the image of evolution as a tree.

But gene evolution is not the same as species evolution. Of course, evolution is not as simple as Darwin thought, and in some aspects it looks more like a confusing web than a tidy tree. There are branches that are weirdly connected one with another (like when some bacteria entered old cells to become our mitochondria and chloroplasts). Maybe the tree has more than one root (there is evidence for several "origins of life" that later became connected).

Maybe the tree metaphor will change, or will be substituted by a web. But from that to proclaiming "the end of Darwin" or biology's next great revolution, there's a long way to go.

(translated by Adrián Robles Benavides)

To receive Science for pleasure weekly
in your email, subscribe here!

Do species exist?

by Martín Bonfil Olivera
Published on Milenio Diario, March 4, 2009

Lots of people find their fun trying to demonstrate that science's big theories are wrong. Einstein's relativity and Darwin's evolution by natural selection are two old time favorites.

Since science does not offer absolute truths, but simply knowledge that is reliable and useful, but that is in constant evolution, there's always the possibility that these critics are right. However, the usual thing is that, to begin with, they don’t have a good understanding of the theories they intend to overthrow.

One of the most common misunderstandings of Darwin's theory is the definition of a biological species. His book On the origin of species shows how they emerge, but Darwin's explanation —the varieties that appear within the same species are actually "incipient species" which, little by little, can get separated from the original— sound looks confusing. A species turns into another? When can we precisely talk about a new species? What is the difference between species, subspecies, varieties and race?

The problem is that we do not normally think in terms of populations, but of individuals. A friend of mine says he is convinced that there had to be a first human being, born from a "still not human" mother. He thinks that between both species —human and pre-human— there is a well defined border that can be crossed in one step (like the mutation that originated the Ninja Turtles)

The idea is not a dumb one: these first individuals of a new species were known as "hopeful monsters" for a long time. But, although their existence is possible, they are extremely rare cases. The normal way of things in evolution, by far, is the gradual accumulation of minimum changes that make the task of defining when a variety turns into a new species as hard as saying with precision just how many hairs a man must loose to call him bald.

In his revealing book Darwin's dangerous idea, philosopher Daniel Dennett explains that in reality, what allow us to distinguish between one species and another is the absence of intermediate individuals between two populations. When there is continuity between both, we realize that the definition of species is, in reality, a human abstraction. We'll talk more about this.

(translated by Adrián Robles Benavides)

To receive Science for pleasure weekly
in your email, subscribe here!

Darwin, wrong?

by Martín Bonfil Olivera
Published on Milenio Diario, February 18, 2009

A kind but pressing reader is worried because, by reading what several science writers, including me, have published about the ideas of Charles Darwin, and comparing it with what he wrote in his books On the origin of species and The descent of man, he finds discrepancies.

He is concerned because some sentences from Darwin can be read to say that human beings are superior to other species, and that they descend from monkeys (which is of course wrong: man and money descend from the same ancestor, not from one another; moreover, species can be well or badly adapted to their environment, but there can be no talk of superiority in absolute terms).

Although Darwin did not say that, he did write things that we now know to be wrong. In part because in later editions he incorporated some changes as a concession to criticism from religious thinkers, changes that introduced confusion in some terms.

On the other hand, in the 150 years since the publication of The origin, knowledge has advanced a lot. The mechanism of inheritance, a key component of his theory of evolution by natural selection, was unknown. For lack of a better explanation, he proposed a hypothesis (pangenesis) to explain it; he was wrong. The correct mechanism —genes— was discovered by the monk Gregor Mendel around the same time Darwin was publishing his book, but it was forgotten and was not re-discovered until 1900.

Genetics was incorporated to Darwinian theory and gave rise to population genetics, and the modernization of evolutionary theory continued during the 30's and 40's up to the "modern synthesis" or synthetic theory of evolution.

Finding ideas that sound wrong in Darwin's texts shouldn't come as a surprise: like any scientific theory, his has been corrected, refined and elaborated. If Darwin could read a modern evolutionary biology book, he would be surprised, but not worried: he'd be happy to see that, far from being taken as an unmoving dogma, his ideas have been part of the evolutionary process that gives science its power not to find absolute truths, but to generate theories in constant change that aspire to describe, in the best way possible, the natural world.

(translated by Adrián Robles Benavides)

To receive Science for pleasure weekly
in your email, subscribe here!

A Toast to Darwin!

by Martín Bonfil Olivera
Published in Milenio Diario, February 12, 2009

Today is the big day. We celebrate that 200 years ago, Charles Robert Darwin was born. Fifty years later he would publish On the origin of species by means of natural selection or the preservation of favoured races in the struggle for life, the book that turned biology into a full blown science, giving it the conceptual backbone that supports and gives sense to the whole of biological knowledge.

We celebrate the man, but we must also celebrate the idea (an idea that another man, Alfred Russell Wallace, also had, although sadly he will not receive any tributes: history only remembers first places, not seconds).

Darwin's great idea —natural selection as the mechanism that allows species to change, adapting to their environment— has turned out to be, during these 150 years, very polemic. This is due to three public-relations problems it has.

First off, it's an idea that, although simple —the better adapted organisms inherit their advantages to their descendants, which become predominant in the population— is anti-intuitive. Selection allows advantageous changes, produced by chance and inherited from parents to descendants, to accumulate. The reiterated variation-selection process produces, with time, designs that appear to be the product of an intelligence. It is hard to accept that complex creations such as the wing of a bird or the human brain —and the mind— are the results of a blind mechanism.

Second, Darwin's idea is naturalistic: compared to religion, it gives a completely natural —almost mechanical— explanation to the wonderful variety and amazing adaptations of living beings. To abandon a simple and comforting explanation (creation by a superior being) and substitute it by a natural process can be seen as a threat to religious faith. Maybe it is.

Finally, Darwin's idea is powerful. It's applicable not only in biology, but in economy, computing, cultural studies, medicine, chemistry, engineering, sociology, philosophy… That's why it's been described as "dangerous".

However, no matter the reluctances, today, the importance of this idea is undeniable, and its applications are more important every day. That's why Darwin well deserves that we toast to his memory. Cheers!

(translated by Adrián Robles Benavides)

To receive Science for pleasure weekly
in your email, subscribe here!