- 4 months ago
Beyond “The Selfish Gene” to “The Selfish Network”
The grasshopper is the gene, and the locust is the networked swarm.
David Dobbs has a very interesting article out in Aeon about the incompleteness of “selfish gene” theory and the rise of an idea called “genetic accommodation”. Accommodation is the appearance of a trait, say larger muscles or faster running, in response to the environment, within a single generation (it sounds Lamarckian, but it’s not). Dobbs’ article is full of some pretty high-level biology, but it’s a very crucial lesson on the realities of natural selection in complex creatures and complex populations.
Chances are, if you’re a student of genetics and evolution, you know about Richard Dawkins and “the selfish gene”. This theory, and the book of the same name, places the gene at the center of evolution, and presents the organism, you or I, as vehicles for their replication and selection. It is beautifully written, well thought-out, and it made Dawkins the star he is today.
Unfortunately, the idea of “selfish genes” is incomplete, at least according to many modern evolutionary biologists. In complex creatures, there are a host of changes in appearance, ability and behavior (so-called “phenotypes”) that do not result from discrete genetic mutations, but rather from changes in how those genes are expressed, and these often show in the same generation, not just in offspring.
Dobbs gives us the example of the locust and the grasshopper, which ( I did not know this), are the same species! When food goes scarce, the lone hopper morphs into a swarming species that can lay waste to fields at Biblical proportions. These changes are not at the level of DNA changes within the gene, they manifest in how that DNA is read and turned into proteins or whatever the gene product turns out to be.
There are two important keys here: 1) Genomes are full of mutations and differences, most of which are silent and don’t contribute to natural selection, and 2) in complicated creatures such as us, genes are subject to complex, squishy, variable networks, and it’s mutations in many genes within and between networks that often lead to phenotypes.
That’s an incomplete oversimplification itself, but if you’d like to dig deeper, read this PZ Myers piece on how evolution is about networks. As for me? I’ve studied molecular genetics for about ten years now, and while Dobbs is right that the simple “selfish gene” idea needs work, gene expression differences are also dependent on genes, and those genes can be mutated and selected, or not, so after a while this whole networked snake begins to eat its own tail.
Evolution is hard. Most people, if they even accept it, don’t get far enough in biology classes to see just how hard it is. In school, we begin our study of genetics with the study of Mendel’s peas, a simple and idealized example to demonstrate how statistics and ratios are at play in the distribution of genes. But then almost instantly, if we go on with our studies, we learn that these idealized scenarios are incomplete, and that’s not how the real world of natural selection and population genetics works. So we look for where our rules are broken, and we apply new, often complex, rules to fill in the gaps.
This is how science itself works. Our idealized classroom scenarios, like Dawkins’ “selfish gene” or Mendel’s peas, are important tools to have in our toolbox, but they are incomplete. It is important that learn to identify their deficiencies, and to use new observations to create new tools … and with them we are always working to build a better house.
Which we then hope is not flattened by a locust swarm.
Check out Die, Selfish Gene, Die by David Dobbs. What do you think?
- 5 months ago
- 6 months ago
How many planets? is an interactive feature from New Scientist detailing the late Kepler exoplanet-hunting spacecraft’s planetary haul.
Kepler focused its gaze on a tiny piece of the sky near the constellation Cygnus, about 150,000 stars. By looking for small dips in a star’s intensity caused by a planet orbiting in front of it, the Kepler team tallied 3,588 possible exoplanets.
By then throwing out all the big boys that are nothing like Earth (down to 1,696) and then focusing on the planets that are in their star’s habitable zone (where the conditions could allow for liquid water on its surface), they narrowed it down to 51 possible Earth-like exoplanets.
Not that many, eh? Well, keep in mind that Kepler would miss planets who weren’t in the right orientation or orbited dim stars. A few calculation corrections tick that number up to 22,500…
Finally, Kepler was only looking at 0.28% of the sky. Expand it to the whole of the Milky Way, and you get something like 15-30 billion possible Earth-like planets. (I want to emphasize the possible there, because really, who knows?)
Kepler may be gone, but I can’t wait to see what future planet-hunting missions, using different detection strategies like gravitational distortion and newer imaging equipment, can find. Earth is definitely not alone. The real question for our time is this: Are we alone?
Explore the full interactive at New Scientist. For more exoplanet explorations, check out Lee Billings’ new book Five Billion Years of Solitude: The Search For Life Among The Stars
- 7 months ago
Dr. Donald Low, public face of Toronto SARS crisis, dies
Dr. Donald Low, a leading Canadian infectious disease expert who rose to prominence while helping Toronto cope with the SARS crisis that killed hundreds worldwide a decade ago, has died at age 68 after being diagnosed with a brain tumour.
Low was the microbiologist in chief at Toronto’s Mount Sinai Hospital and a professor at the University of Toronto.
A great man. A great loss for our lab and for microbiology.
In a tiny insect called the Issus.
When it prepares to jump its legs lock into the jump position. At the top of its legs, a minuscule pair of gears engage—their strange, shark-fin teeth interlocking cleanly like a zipper.
- 7 months ago
- 7 months ago
We Must Protect This House
It’s like a maypole erected within a barbed wire fence! Not only does the central pole have several “guy-wire” support strands keeping it up, but the outer poles have horizontal strands strung between them, just like our fences. It’s almost certainly a defense mechanism against ants or other predators for whatever is incubating inside. What an amazing evolutionary feat!
Several commenters at Why Evolution Is True believe it is either the egg sac of a mystery spider or a very elaborate moth cocoon. While some moths have been known to erect Stonehenge-like fences around their cocoons, I lean more toward the spider theory.
Moth cocoons (like this incredible lace-like cage observed by Destin from Smarter Every Day) are spun by the caterpillar that is cooking inside, and I just can’t see a way that this silk was spun by the resident. It’s just too elaborate. More likely that a spider built her babies this safe little home and then sailed away. Ideas?
Other theories: Tiny Area 51, Insect Isengard, air traffic control station for jungle birds.
Ahh, I could kiss you, evolution.
- 9 months ago
Gone are the days when we could comfortably assume that a single gene or hormone is responsible for a complex disease or behavior. As new data roll in, previously clear-cut cases turn out to be more complex. One such case is oxytocin, a neurohormone closely related to prosocial, bonding behavior…
Find out more by clicking the title above.Source: science