The evolution of language

Language has families, too

We think of English as being a language distinct from, say, Hindi, but they both belong to the Indo-European family of languages. Family members include French, Spanish, German, and Walloon, spoken in a tiny area of France and by descendents of settlers in Green Bay, Wisc. Language, like genes, is passed on from generation to generation, and through time undergoes changes and additions, just as genomes do.

In the 1950s, a linguist named Morris Swadesh developed a field known as lexicostatistics, which studies linguistic family trees through quantitative analysis of a core group of words. These 100 to 200 words, known as Swadesh lists, identify the commonalities in any language, and according to Swadesh’s ideas, were thus less likely to change over time. To trace language lineages, Swadesh compared these groups for similarities and words—cognates—that appeared to have a common ancestor. The more cognates two languages shared, the more closely related they were presumed to be.

A fun word to learn: Glottochronology

In a study published in Nature, authors Russell Gray and Quentin Atkinson take the Swadesh approach into the realm of glottochronology, a way of determining the timing of divergence of languages. Based on their computations, they determined that the root of the Indo-European family tree traces back almost 9000 years ago to an area of what is now Turkey, where farmers grew crops and spoke Hittite. As they migrated, they took their languages with them. Gray and Atkinson’s findings counter another proposed origin of the Indo-European family tree, which posited that invading horsemen from the steppes of Asia brought their language with them as they prosecuted their warlike endeavors 6000 years ago.

What does this have to do with biology?

It is both inspired by and inspiring to biological evolutionary study. Swadesh developed his ideas at about the time that Watson and Crick were making their startling elucidation of DNA structure and copying mechanism. In their analyses, Gray and Atkinson used tools very similar to those biologists use to develop phylogenies to explore how species are related. Instead of gene or amino acid sequences, the authors used a series of letters that formed words; instead of identifying mutations, they identified changes in letters or syllables; and instead of orthologues—genes derived from a common ancestor—they identified cognates to elucidate relationships.

But Swadesh preceded biologists in one sense, in that he proposed using his analyses of Swadesh lists to determine time lapses as language developed and diverged; in other words, to use any divergences in cognates as a sort of clock to measure the time over which changes occur. One of the basic assumptions of this approach is that the changes will occur at a relatively constant rate when averaged out over time, giving a reasonably accurate assessment of how far back a relationship can be traced. This idea was only later taken up in biology as the idea of the “molecular clock,” in which biologists use the presumption of a constant rate of change in some gene or amino acid sequences to infer the timing of genetic divergence.

Problems with either approach

There are, of course, problems with either approach, and again, the problems are remarkably similar, whether the field is biology or linguistics. One common problem in building phylogenies is determining which changes occur because of environmental similarities (convergence), instead of relatedness; convergence is also an issue in the linguistic analysis, where words may appear to be cognates when they really are not. Another question that arises in biology is whether or not the genes being examined are suitable markers of evolutionary change; again, the same problem arise in linguistics—are words in the Swadesh lists, for example, suitable choices for comparison among languages? In spite of these inherent problems, Gray and Atkinson’s work has opened up fresh avenues of discovery and debate and brings biology and language closer to one another than ever.

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Platypus spur you? Grab a scorpion

The most painful egg-laying mammal: the platypus

The duckbill platypus is an impossible-looking, risible creature that we don’t typically associate with horrific pain. In fact, besides its odd looks, its greatest claim to fame is that it’s a mammal that lays eggs. But that’s just because you’re not paying close enough attention. On the hind legs of the male platypus are two spurs that inject a venom so painful, the recipient human writhes for weeks after the encounter. In spite of the fact that platypuses (platypi?) and humans don’t hang out together much, platypus venom contains a specific peptide–a short protein strand–that can directly bind to receptors on our nerve cells that then send signals of screeching pain to our brains. Ouch.

Hurting? Reach for a scorpion

If you’ve ever experienced platypus-level pain and taken pain killers for it, you know that they have…well…side effects. It’s because they affect more than the pain pathways of the body. The search for pharmaceuticals that target only the pain pathway–and, unlike platypus venom, inhibit it–forms a large part of the “rational design” approach to drug development. In other words, you rationally try to design things that target only the pathway of interest. In this case, researchers reached for the scorpion.

Their decision has precedent. In ancient Chinese medical practice, scorpion venom has been used as a pain reliever, or analgesic. But as developed as the culture was, the ancient Chinese didn’t have modern protein analysis techniques to identify the very proteins that bind only to the pain receptors and inhibit their activity. Now, a team from Israel is doing exactly that: teasing apart the various proteins in scorpion venom and testing their ability to bind pain receptors in human nerve cells.

The next step? Mimicry

With proteins in-hand, the next step will be to create a synthetic mimic that influences only the receptors of interest. It’s a brave new world out there, one where we wrestle proteins from scorpion venom and then make copycat molecules to ease our pain.

For your consideration

Why do you think the platypus makes proteins in its venom that human pain receptors can recognize if humans generally haven’t targeted platypuses (platypi?) as prey over its evolution?

In the human body, a receptor may be able to bind each of two closely related molecules–as a hormone receptor does with closely related hormones–but one of the molecules activates the receptor, while the other molecule inhibits it. Taking this as a starting point, why do you think some proteins in scorpion venom–which often causes intense pain–have the potential effect of alleviating pain?

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