A couple of teaspoons of dried yeast. A pinch of sugar. A cup of warm water. And a few minutes later, you’ll have a foamy, bubbly brew of lively yeast cells, ready to be added to a bowl of flour and turned into bread.

Kirsty Wigglesworth/Associated Press A pint of beer in a London pub.

Saccharomyces cerevisiae, also known as baker’s yeast, is one of the most useful beings known to humans. We rely on it for making bread and beer; but it is also a denizen of the laboratory, one of the most studied organisms on the planet. Which is why I’m nominating it for Life-form of the Month: June.

But what is it? Yeasts are fungi — so they are related to mushrooms. And fungi are, strangely, quite close relations of ours. Or at least, they are more closely related to animals than they are to plants. Like animals, they digest their food — though fungi do it not by swallowing, but by releasing chemicals into the environment. The chemicals break down the food — like rotting wood — into smaller molecules, and the fungus then imports these smaller molecules into its cells.

Sometimes this takes on sinister dimensions. For example, if you are nematode worm crawling through the soil, you may get stuck in a sticky web. But in this web there is no spider. The web itself is alive: it is not made of silk, but of the filaments of a fungus. The web itself will digest you. Other fungi set snares — they produce rings of cells that swell up when a worm passes through, catching it round the middle. The fungus then digests the worm at its leisure.
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Felix Borner An aerial view of the wildebeest migration in the central Serengeti National Park, Tanzania.

Imagine. You are lying in the grass in the east African savannah, watching wildebeest fording a shallow river. You can hear the funny grunting noises they make, and as they pass by, you can feel the impact of their hooves on the ground and smell their rich animal smell. You see their kicking heels, their beautiful sleek bodies. Then you look up, and you realize that the herd stretches as far as you can see, that the plain is dark with wildebeest. If you were to wait for them all to pass, you would be there for days.

The sight is magnificent, primal and profoundly moving. It is the wildebeest migration.

Every year, more than a million wildebeest, along with hundreds of thousands of zebras and gazelles, move through the Serengeti-Mara ecosystem of Tanzania and Kenya, following the rains. In the course of a year, an individual wildebeest may cover as much as 2,100 kilometers. (That’s more than 1,300 miles — which is further than the distance between New York and New Orleans.) It is the last great migration on Earth.

But for how much longer? A large part of the migration takes place within the vast Serengeti National Park in Tanzania, and there are reports that the Tanzanian government is preparing to build a major road through the northern part of the park: through a designated wilderness area, through the migration route.
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In 1884, a man called Francis Galton opened the doors of his “Anthropometric Laboratory.” This was “for the use of those who desire to be accurately measured in many ways, either to obtain timely warning of remediable faults in development, or to learn their powers.” The many ways included height, hand strength, acuity of sight and hearing, lung capacity and the power of a blow with the fist.

Galton was one of Charles Darwin’s cousins. This was no particular distinction: Darwin had many cousins. Indeed, he married one, and was married by one — the vicar who presided at the wedding was a cousin too. But Galton was distinguished in other ways: he was one of the great scientists and polymaths of the 19th century.

Among his achievements: he was the first to make rigorous weather maps, and he discovered the anticyclone. He developed methods to describe and classify fingerprints, and showed that they were a reliable way of telling one person from another. He made major contributions to statistics, discovering the concept of correlation and calculating the first correlation coefficients. (We talk of correlations when disparate phenomena occur together, either because one causes the other — as in smoking and lung cancer — or because both are the result of some other factor. For example, people with red hair tend to have pale skin; both are due to a particular gene involved in pigmentation. Correlation coefficients are a measure of the strength of the association.) Read more…

A few weeks ago, I was walking through a wood in the English countryside when I heard the unmistakable call of the cuckoo. For some reason, it caused me to fall into a reverie, and as I walked, I began to meditate on that iconic bird and what it represents.

The European cuckoo (Cuculus canorus) is, famously, a “brood parasite”: the female lays her eggs in other birds’ nests. Typical victims are small birds like reed warblers and wagtails. When the young cuckoo hatches, its first act is to dispose of any other eggs: it heaves them out of the nest, leaving itself as the sole occupant.

What happens next is peculiar. The foster parents don’t appear to notice they are rearing a monster. Instead, they work hard to satisfy the demands of the chick, even though it sometimes becomes so large that it no longer fits inside the nest, and has to sit on top. It’s one of the oddest sights in nature.

Roger Wilmshurst/Photo Researchers, Inc. A reed warbler brings food to a young cuckoo that hatched in the warbler’s nest, an example of brood parasitism.

The cuckoo habit has evolved several times. It’s found in species as diverse as cowbirds, indigobirds, honeyguides and even a species of South American duck.

(Actually, brood parasitism can also occur within a species — geese sometimes slip an egg into a neighbor’s nest, as do coots and starlings. Nor is it restricted to birds — fish and insects sometimes foist the rearing of their offspring onto others. But for the rest of this article, I want to focus on the birds that are “professional” brood parasites — the ones that, like the cuckoo, never build nests, and always palm their offspring onto another species.)
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Intelligent design. That’s one goal of synthetic biology, a field that was catapulted into the news last week with the announcement that a group of biologists had manufactured a genome that exists nowhere in nature and inserted it into a bacterial cell. The dream is that, one day, we’ll be able to sit and think about what sort of life-form we’d like to make — and then design and build it in much the same way we make a bridge or a car.

Realizing this dream is still some way off. But before I get to that, let me briefly describe the state of play.

Synthetic biology is predicated on the fact that, to a large extent, organisms can be broken down into a set of parts. For example, the information contained in DNA comes in discrete chunks — namely, genes. Genes contain the instructions for making proteins — molecules that come in different shapes and sizes — as well as information about where and when those proteins should be used. Proteins interact with each other, driving many of the functions of the cell.

Some genes are essential: without the proteins they encode, the organism cannot exist. But many genes are “optional” — in the laboratory at least, the organism gets on fine without them.

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Fernley | Dreamstime.com Archaea were first found in areas like Bumpass Hell in Lassen Volcanic National Park, where fissures and volcanic heat created hot springs.

It’s that time of the month again. Yes: it’s time for Life-form of the Month. In case you’ve forgotten, this coming Saturday is International Day for Biological Diversity, a day of celebrations and parties to appreciate the other occupants of the planet. So if you do nothing else this weekend, drink a toast to “Other Life-forms!” In honor of this event, my nomination for Life-form of the Month: May is a group of abundant and fascinating beings that are undeservedly obscure: the archaea.

Say who?

Archaea are single-celled microbes with a reputation for living in tough environments like salt lakes, deep sea vents or boiling acid. One strain can grow at temperatures as high as 121 degrees Celsius (249.8 degrees Fahrenheit), a heat that kills most organisms; others thrive at the seriously acidic pH of zero.

They are not restricted to life at the fringes, however. As we have learned how to detect them, archaea have turned up all over the place. One survey estimated that they account for as much as 20 percent of all microbial cells in the ocean, and they’ve been discovered living in soil, swamps, streams and lakes, sediments at the bottom of the ocean, and so on. They are also routinely found in the bowels of the Earth — and the bowels of animals, including humans, cows and termites, where they produce methane. Indeed, the archaeon known as Methanobrevibacter smithii may account for as much as 10 percent of all the microbial cells living in your gut.
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The past comes to us in tantalizing fragments — a bone here, a footprint there. But of all the fragments yet discovered, perhaps none is so tantalizing as the one published in the journal Science last week: the Neanderthal genome.

Neanderthals have perplexed and intrigued us ever since the first bones were discovered in a cave in what is now Germany, in 1856. Who were they? Why did they vanish?

James Estrin/The New York Times A reproduction of a Neanderthal skeleton, left, and a modern Homo sapiens skeleton, right.

Over the past century and a half, our picture of them has become less blurry, more distinct. From their bones we know that Neanderthals were bigger and stronger than us “anatomically modern humans,” and they had larger skulls that boasted prominent eyebrow ridges. They appear to be the descendants of a lineage that separated from ours around 400,000 years ago, wandered out of Africa, and lived across Europe and central Asia. The last of the Neanderthals lived on the Iberian peninsula, dying out sometime between 37,000 and 28,000 years ago. Read more…

The lights go down. The room fills with music — a pulsating hip-hop rhythm. And then, over the music, you hear the voice of Richard Dawkins reading a passage from “On the Origin of Species” by Charles Darwin: “Whoever is led to believe that species are mutable will do good service by conscientiously expressing his conviction. For only thus can the load of prejudice by which this subject is overwhelmed be removed.”

Baba Brinkman.

So begins one of the most astonishing, and brilliant, lectures on evolution I’ve ever seen: “The Rap Guide to Evolution,” by Baba Brinkman.

Brinkman, a burly Canadian from Vancouver, is a latter-day wandering minstrel, a self-styled “rap troubadour,” with a master’s degree in English and a history of tree-planting (according to his Web site, he has personally planted more than one million trees). His guide to evolution grew out of a correspondence with Mark Pallen, an evolutionary biologist and rap enthusiast at the University of Birmingham, in Britain; the result, as Brinkman tells us, is “the only hip-hop show to have been peer-reviewed.”
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The placebo effect is, potentially, one of the most powerful forces in medicine. The challenge is to harness that power in a reliable and systematic way.

First, what is the placebo effect?

It’s the improvement in health that some patients experience because of the feeling that they are receiving medical care. A classic example comes from drug trials. Suppose patients are randomly divided into three groups: those who get no treatment, those who get the drug that’s being tested, and those who get the placebo treatment — typically a pill that looks and tastes like the drug, but doesn’t contain it, or any other active ingredient.

The idea is that the “no treatment” group shows how many people would have gotten better by themselves; the “placebo” group shows any effect of participating in medical rituals (like taking pills); the “drug” group shows any effect of the drug over and above the effect of medical rituals. Simple.

Or not. Different studies of the placebo effect report wildly different results. One survey of 117 trials of two ulcer drugs found that, depending on the trial, patients in the placebo group had anywhere from zero to a 100 percent recovery rate.

The drugs also varied in their effectiveness from one trial to the next; sometimes patients on the placebo did better than those on the drug. Intriguingly, the results varied from country to country, with Brazilians showing no placebo effect and Germans having a strong one. Why? No one knows, but it doesn’t appear to be because of anything inherently German: trials of drugs for hypertension found a weaker placebo effect in Germany than in other countries.

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