I hope for this to be a recurring theme on the blog here: looking at recent scientific developments, or age-old scientific arguments, about biology. In particular, I find the theory of evolution and its opposers extremely intriguing. Perhaps I’ll expand on that another day. In the mean time, here are some interesting stories related to the world of biology from the last week.
Of Fish and Flies: The Evolutionary Role of Genes
The NPR takes a look at the role that genes, and gene expression, play a role in evolution. The stickleback fish and its many varieties are considered. David Kingsley, a biologist from Stanford University, discusses how the stickleback found in environments with a large number of insects typically have less spines: insects eat sticklebacks by attaching them to those spines. So it follows that those who grow less spines in that environment have a fitness advantage and are able to propel their genes on into the future. Having found the gene responsible for building these spines, Kingsley also discovered that the gene plays a role in the development of the brain, jaw, and in the hind quarters. Even more intriguing, the roughly identical gene is found in all sticklebacks; the difference between the varities is how and where the genes are activated or switched on.
The journalist then takes up a conversation with Sean Carroll, the author of Endless Forms Most Beautiful and, more recently, From Eternity to Here. Carroll gives a similar example to that of the stickleback, arguing that fruit flies living at higher altitudes are darker than their lower-altitude counterparts because of a genetic mutation changing how these genes are expressed. As Carroll puts it:
“If we take a big picture of our genome,” says Carroll, “only about 1 1/2 percent of the 3 billion letters of our DNA code for proteins. And we think that several more percent is involved in doing just this. Of controlling how those genes that encode proteins are being used.”
Meat may be the reason humans outlive apes
Of interest to biologists is a simple fact of life: if homo sapiens sapiens share 95-98% of their genes with their great ape relatives, why is it that humans are capable of living to 70+ while great apes almost never crack the 50 year mark? In the Western world, we could seemingly attribute this discrepancy to advances in technology, in particular the rapid advancements in medical science in the last 200 years. Still, those living in what we could consider to be more archaic lifestyles (a la hunter-gatherer/forager) have a lifespan that exceeds that of the great apes. What could account for this?
It has long been suggested that eating meat played a central role in our presently evolved brains. With a diverse food supply, not only do we have a greater selection of nutrients with which our bodies may be fueled, but also we must be capable of understanding and finding a much larger range of delectables. As a simple example: an animal that needs to make a mental catalogue of what’s safe, what’s tasty, what is easy to find, for both meat and legumes would almost certainly require greater processing power than a herbivore. Biologist Caleb Finch at USC suggests that meat also played a role in our improved life expectancy.
Finch argues that many moons ago, our new found diet of raw red meat brought with it a new challenge: chronic inflammation. To combat this, the humans that evolved a particular cholesterol transporting gene, ApoE3, were more likely to survive, and thus this gene has spread to virtually all of the human population. ApoE3 appears to lower your risk of contracting heart disease and Alzheimer’s disease, and is correlated with longer lifespans.
Surprising sea slug is half-plant, half-animal
A recent discovery was made of a rare animal: one that produces chlorophyll, a pigment normally found in plants only. With this ability in their pocket, the sea slugs Elysia chlorotica are capable of doing photosynthesis, a process that allows the slugs to convert sunlight to energy. The sea slug is thus able to acquire the energy necessary for living. Though it seems that such an ability, which can be passed on genetically, would allow the slugs to live without eating, but they cannot use the chlorophyll to do photosynthesis until they’ve “stolen” the necessary chloroplasts from algae that they’ve consumed. Though this ability to produce chlorophyll can be inherited, it is not clear how they’ve acquired this genetic material in the first place.
This story was of particular interest to me. About two weeks ago, I was listening to a debate on YouTube between a geneticist and the famed Young-Earth Creationist Kent Hovind. Hovind asked the gentleman (I’m afraid I don’t remember his name) what would disprove the theory of common ancestry, and this geneticist responded that finding plant DNA in a multi-cellular animal would disprove it. My first thought was that this wouldn’t disprove common ancestry by a long shot. Instead, it raises questions about what common ancestor these slugs share with plants or, as seems more plausible, how the slugs were able to acquire this genetic information. That there is an instance of evolution where we don’t know the mechanism really does no damage to common ancestry or evolution as a whole; it simply raises questions about what mechanisms can do what, and which play the biggest role. The totality of evidence still supports evolution and common ancestry, and it will take a lot of work to unravel that thread.
In monkey babble, seeking key to human language development
The NYT does a fantastic job reviewing the concept of primate language. It is argued that if we can find some markings of language in other species, we can gain insight into how the complex language shared by humans could have evolved. In past experiments, we’ve been able to get primates to use human language to a limited extent (the strongest example being that of sign language). Similarly, we’ve found what appears to be a sign of animals having their own very rudimentary language: Vervet monkeys have specific alarm signals which are called out. When these signals were recorded and played back, the monkeys responded as if there were a predator to be concerned about. Though these verbal signals do not have anywhere near the complexity of human language, there do seem to be specific noises associated with specific meanings.
The bulk of the article gives examples of Dr. Zuberbühler’s finding that specific noises are correlated with specific meanings, contrasting this proto-language with the simple fact that chimpanzees have no clear language of their own; you would think that they would having shared a recent common ancestor with other apes and monkeys. While we are a long ways away from identifying a clear evolutionary model for the neural mechanisms through which language came to fruition, we seem to be just scratching the surface, with many discoveries yet to come so long as we stay the course.