IN NUMBERS
56
The percentage of green turtle nests lost from Florida’s Archie Carr National Wildlife Refuge, after Hurricane Irma.
289
The number of species of Japanese marine life that have washed up in the US on debris from 2011’s tsunami.
1,300 The length, in kilometres, of the Deep Underground Neutrino Experiment, which is currently being built.
Did Homo sapiens and Neanderthals interbreed? How are calories in food calculated? Calories are a measure of the energy content of food, and as such play a key role in the science of nutrition. During the late 19th Century, scientists began the laborious task of measuring the calorie content of food by burning it in a sealed container and measuring the heat released. While studying the results, a rule of thumb emerged: weight for weight, fat contains nine calories per gram, around twice that in protein or carbohydrates. This led to the so-called Atwater system for calculating the calories in food without lab tests: work out the proportions of fat, protein and carbs it contains, and multiply by the relevant ‘Atwater factor’ giving the calories contained in each component. But while it’s quick and cheap, there’s growing concern the Atwater system misses subtleties of how the body uses calories. RM
Yes, and more than once! DNA analysis suggests that the earliest encounter between the two species was 100,000 years ago, just as the earliest wave of Homo sapiens was migrating out of Africa. They met Neanderthals moving eastwards from Europe to Asia and swapped genes. Later interbreeding periods happened 55,000 and 40,000 years ago, and each time we acquired some Neanderthal genes. Unless you are of sub-Saharan descent, your genome contains 1-4 per cent Neanderthal DNA. LV
THE THOUGHT EXPERIMENT
PHOTOS: GETTY X3, ALAMY X2, SHUTTERSTOCK ILLUSTRATIONS: RAJA LOCKEY
WHAT WOULD HAPPEN IF ALL THE TREES WERE CUT DOWN?
1. THE LOGISTICS
2. ECOSYSTEM COLLAPSE
There are three trillion trees in the world. The timber industry currently cuts down 15 billion a year, so at current rates it would take at least 200 years to fell them all – probably much longer because a lot of virgin forest is hard to reach. If you gave everyone aged 15 to 65 a chainsaw, they would have to cut down 625 trees each, which might be manageable in a year. But collecting and processing that timber would take much longer and 99 per cent of the trees would just lie on the forest floor, rotting and releasing 35 billion tonnes of CO2.
Eighty per cent of land animals and plants live in forests and without the trees most of them will die. Trees also keep the ground wet and cool, and help to drive the water cycle. A large tree can push 150 tonnes of water into the atmosphere each year, which then falls back on the forest as rain. With no trees, the land will heat up and dry out and the dead wood will inevitably result in enormous wildfires. This will fill the sky with soot that blocks out the Sun, causing failed harvests for several years and leading to worldwide famine. Vol. 10 Issue 2
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