National Museum of Natural History, Washington DC, and Smithsonian Tropical Research Institute, Balboa, Republic of Panama

An archaeologist tells how her research interest sheds light on the history of her favourite fruit.

My mother gave me a lot of sage advice during my childhood. This sometimes countered prevailing wisdom, such as her recommendation that I should eat bananas, not apples, every day.

The nutritional qualities of bananas were underappreciated when I was growing up in Philadelphia, Pennsylvania, although their value as a crop had been recognized millennia before.

A recent paper (B. Lejju et al. J. Archaeol. Sci. 33, 102–113; 2006) reports that bananas were being cultivated in Africa as long as 5,000 years ago.

The investigators reached this conclusion by studying phytoliths — highly durable pieces of silica that form in plant cells — that had been dug up in Uganda. I use phytoliths (and starch grains) in my own research into the history of agriculture, so it was more than just my fondness for bananas that drew me to this paper.

Phytoliths tell us which crops grew where and when, and so in turn can teach us about human cultures. Part of what makes this finding interesting is that bananas aren't native to the African continent. Wild bananas grow in eastern Asia, Australia and Melanesia. Hence the Ugandan bananas represent ancient human transport, probably through trade across the Indian Ocean with societies that were already growing the plant.

The age of the banana phytoliths also rivals presently available dates for the domestication of important, indigenous plants such as sorghum. However, I suspect that when phytolith and starch-grain analysis is applied to the history of native African crops, the date of their domestication will be pushed further back.

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Scripps Institution of Oceanography, La Jolla, California, USA

A marine biologist sees the potential of cyanobacteria, and the benefits of their renaming.

Let's start with a false syllogism: bacteria are prokaryotes, blue-green algae are prokaryotes, and therefore blue-green algae are bacteria. All other algae are eukaryotes and so, the argument went, we should reclassify the Cyanophyta as cyanobacteria.

I was never in favour of this renaming, but it may have been good for funding. I've heard that grant applications for research on bacteria have better chances of success than those for research on blue-green algae.

And these oft-neglected organisms have a lot to offer. A recent paper on Lyngbya majuscula from Bill Gerwick, now at the Scripps Institution of Oceanography in La Jolla, California, and his colleagues (B. Han et al. J. Nat. Prod. 69, 572–575; 2006), for example, reveals some interesting new compounds.

L. majuscula grows on warm seashores as tufts, which, when they come loose and float away, can stick to swimmers' skin and cause a rash — known as swimmers' itch or seaweed dermatitis.

Gerwick and his team extracted from dried L. majuscula two compounds that may explain its irritant effect. The compounds, aurilide B and aurilide C, are hugely complicated ring-shaped molecules that resemble a toxin previously isolated from sea slugs.

In tissue culture assays, the compounds proved toxic to human and mouse cancer cells. Such natural products can act as starting points for pharmaceutical chemists.

Gerwick's paper refers to L. majuscula as a cyanobacterium in its title and as an alga elswhere in its text, but what's important is the science, not the names.

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University of Arizona, Tucson

A biologist turns his attention to evolution's neglected radiations.

Evolution's spectacular adaptive radiations get a lot of press: Darwin's finches and the Hawaiian silversword plants being textbook examples. These organisms, in adapting to environmental pressures, underwent both rapid speciation and radical morphological change.

Such episodes give rise to easily observable diversity and have stimulated extensive study. But how about those hyperdiverse clades in the tree of life in which many species have little morphological difference between them?

I first pondered this problem when musing about my thesis on the flowering-plant taxon Astragalus. I was cursed with perhaps 2,500 species, many remarkably similar. Their small differences were typically of uncertain adaptive significance.

Alas, I have counted barely ten papers since then that have addressed such radiations, which end up being labelled as 'non-adaptive'. I hope the most recent will shake things up a bit.

It analyses the speciation rate of North American Plethodon, a clade of salamanders most diverse in the woodlands of the Appalachian mountains (K. H. Kozak et al. Proc. R. Soc. B. 273, 539–546; 2006). This group has an evolutionary history that runs back 28 million years and has spun off about 46 species, many of which are only diagnosable by molecular markers.

Remarkably, the rate of speciation in the group's early days matched or exceeded rates seen in the textbook adaptive radiations. This suggests that we have a lot to learn about the evolutionary phenomena driving such radiations.

The authors make some interesting suggestions about the role of geography, ecology and adaptation in the salamanders' evolution. For example, the lineages may have evolved by tracking the ebb and flow of favourable habitats.

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University of Oxford, UK

A physiologist discusses matters close to the heart.

This time last year my father was suffering from congestive heart failure. He became increasingly frail, slowing down like an unwound clockspring until, in February, his heart simply stopped.

As a physiologist, I had some idea of his condition, but I did not then realize how close it was to my own research area.

In 1983, ATP-sensitive potassium (K-ATP) channels were found in the heart. These channels are gated pores that control potassium fluxes across the cell membrane. However, their precise role in the heart was unclear.

One year later, I discovered that these channels are central to the mechanism by which glucose stimulates insulin secretion from the pancreas. Unravelling the role of K-ATP channels in diabetes, and the way in which channel structure influences function, has been an all-consuming passion for me ever since.

To my surprise, it now turns out that these channels also play a role in heart failure. Heart failure is usually caused by narrowing of the arteries, which increases the pressure against which the heart has to pump, making it work harder. Eventually, it fails.

Recently, Andre Terzic of the Mayo Clinic in Rochester, Minnesota, and his group showed that K-ATP channels confer protection against heart failure (S. Yamada et al. J. Physiol. Lond. published online doi:10.1113/jphysiol.2006.119511; 2006). In normal mice, cardiac K-ATP channels open in response to an increased pressure load, reducing stress on the heart. Mice lacking K-ATP channels rapidly develop heart failure and die.

In the pancreas, K-ATP-channel activity is finely balanced: too much causes diabetes and too little hyperinsulinism. But in the heart, as this paper shows, opening is almost always beneficial.

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Royal Holloway, University of London, UK

Methane humour hides serious issues, argues a geologist.

Methane people are like the Jumblies of Edward Lear's poem — far and few, far and few. We work together across continents, sharing air samples in 'round robin' experiments. We also suffer bovine eructation jokes; but it's not just about cows' breath.

Methane is a potent greenhouse gas, produced by wetlands, fossil fuels, grass and forest fires, and rice paddies. But there are major puzzles in the global budget. Methanologists at a recent meeting in Cape Town, South Africa, discussed two of these.

One stems from experiments suggesting that plants emit methane (F. Keppler et al. Nature 439, 187–191; 2006). Our first reaction was 'surely not!', yet satellite studies of tropical forests seem to back up the result. We folk who once energetically sampled the atmosphere on mountain peaks are becoming plant biochemists, watching air bubble through flasks.

Another dispute surrounds methane leaks from fossil fuels. We used to estimate leakage by measuring the carbon-14 in methane. But nuclear power stations release this, so the technique became useless.

Recently, researchers reanalysed methane's carbon-14 record in a way that avoids the nuclear problem (K. Lassey et al. Atmos. Chem. Phys. Disc. 6, 5039–5056; 2006). The result is surprising: roughly 29% of atmospheric methane is fossil — much more than expected. Some of this leakage is geological (that's a worrying puzzle too), but most is from gas and coal industries.

Methane is the quickest, cheapest, easiest greenhouse-gas target. But governments aren't interested. Important monitoring programmes were cut recently in Europe and Australia, and UK regulators even limit industry proposals for leak reduction. Are we looking a gift cow in the mouth?

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