28 April 2012 | NewScientist | 31

vision, usually a feature of predators. Prey have monocular vision for a greater field of view to spot approaching danger.

This great ape would have been relatively slow, without claws, and not very weighty or muscular compared to many prey species. How this human ancestor succeeded, despite its binocular vision, is a major question.Tauranga, Bay of Plenty, New Zealand

Pie and bashFrom Roger PlentyFeedback was puzzled by the term “hand-raised” appearing on a shop sign advertising pork pies (31 March). The notes to P. G. Wodehouse’s novel Sunset at Blandings include a description from Fortnum & Mason, London purveyors of fine food, to the effect that “a raised pie is made as follows: pastry… is moulded round, or raised up, a wooden mould. The mould is removed and the pastry filled with meat… and the contents closed over with pastry again.” So it’s not the pork that’s hand-raised, it’s the pie.Stroud, Gloucestershire, UK

It takes twoFrom Ray GeorgeDiscussing matter-antimatter annihilation, you say “each photon created in this process carries an energy exactly equivalent to the annihilated mass of an electron and its antimatter counterpart, a positron” (31 March, p 33).

An electron and positron usually annihilate to give two photons. Creating just one photon in such an annihilation is impossible because both energy and momentum would not be conserved. Also the particles are not always relatively at rest, so there may also be some kinetic energy to top up the total.Southampton, UK

Feathers or quills?From Tony BrownThe feather-like projections on the back of the pre-dinosaur Longisquama insignis (24 March, p 8) remind me of a defensive feature of much later animals.

Could these “early feathers” have acted in a similar way to a porcupine’s quills? That could explain the thick border on one edge: to strengthen them. A would-be predator would probably leave with a mouth full of these “feathers” instead of the creature itself.New Ollerton, Nottinghamshire, UK

two networks: friends and relatives. I would say most people have at least three, the third being work colleagues, who are mostly not friends or relatives.

It is also not uncommon to be part of two or more networks of friends, perhaps with no other individuals a member of both.Old Fletton, Peterborough, UK

Scared to deathFrom Les HearnDavid Hirst asserts that deaths will have occurred among evacuees from the zone surrounding the Fukushima Daiichi nuclear plant, and implies that these can be fairly blamed on the accident (31 March, p 30).

But Wade Allison, author of Radiation and Reason, has written that evacuation was ordered on the basis of far lower levels of excess radioactivity than can be justified. So the health risk to the ill and infirm of staying put was far less than that of being evacuated, and anyone who died was a victim of a scare.London, UK

Stand up and be…From Wesley ParishKate Douglas discussed why humans became bipedal (24 March, p 36). I see a big gap. When the great ape that was our distant ancestor came down out of the trees and onto the veldt, it had something that very few other prey species had: binocular

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set up – on finding that someone had spent grant money on sun lamps and a swimming pool.Caversham, Berkshire, UK

Intergalactic lasersFrom Michael KellockI am amazed that astronomer Geoff Marcy assumes the most technologically advanced method of interstellar communication available to extraterrestrial beings would be the laser (31 March, p 28).

Instead of limiting our ideas to our own abilities, think of faster-than-light techniques that we can barely imagine, probably using wormholes.

Anyway, if extraterrestrials have been observing us, they will have seen enough reality TV shows to conclude that we are beyond redemption.Foster, Victoria, Australia

Toy Town carsFrom Stuart GoldmanThe idea of driverless cars (31 March, p 19) was originally conceived by Enid Blyton over 60 years ago in her Noddy stories.

The central character owns a car that is capable of driving by itself. I hope the first autonomous model will be finished in chrome yellow with scarlet wheel arches in honour of her prototype.London, UK

The editor writes:n Unfortunately, General Motors beat Noddy to the front of the grid in its Futurama exhibit at the World’s Fair in 1939.

Turtley awesomeFrom Kathryn NelsonIn my appropriately slow-but-steady reading of New Scientist, I have just got round to reading the article on cognitive research in tortoises and turtles (24/31 December 2011, p 44).

It brought back pleasant memories of working as a research assistant in the turtle lab at Bryn Mawr College in Pennsylvania.

The turtles pushed one of two buttons with their noses to earn a squirt of food. They were able to learn some quite complex rules to get their reward. As a lab animal, they were much nicer to work with than the rats I had for my later graduate work.

Why haven’t they been more popular? Perhaps the answer might in small part be due to the fuss an auditor was reputed to have made the year the lab was

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