...that have always intrigued you about the world will appear in this,
your section, and be answered by other readers. Please address
your answers and questions to ‘Curiosities’.

Why do men have nipples?

. The basic model human is one which looks like a pre-pubescent female. People with a single X chromosome are born looking like girls, but never develop sexually. People with XX chromosomes are born looking like girls, and later their extra X chromosome causes their ovaries to produce hormones which make their breasts grow and their menstrual cycle start. People with XY chromosomes are born looking male because their Y chromosome causes them to grow differently as embryos. Later it leads them to produce hormones which makes them grow beards and bigger muscles. They still retain features of the basic model, like breast tissue and nipples, but as they don't normally produce the right hormones, these don't grow as they do in females. If males take female hormones, however, then they grow breasts.

Dr J S Barrett,
London, UK

Why do some cultures write from left to right and others from right to left?

. In ancient cultures, the earliest use of writing was chiefly in public inscriptions. This took the form of engraving on stone with hammer and chisel. Given the perpetual dominance of the right-handed, the hammer would be held in the right hand and the chisel driven from right to left. Therefore the script developed as a right-to-left form. Once estab lished these scripts continued, despite the development of the stylus and slate/clay or the pen and paper where it is easier for the right-handed to 'pull' rather than 'push' the writing implement. Later cultures which inherited these newer 'writing technologies' therefore formed new left-to-right scripts that made for easier use by the right-handed majority.

Francis Boyle,
Yelverton, UK

I've heard that someone has invented a car that runs off chicken manure. Is this true?

. Yes. About 15 years ago a farmer called Bates, I think, who kept many chickens in the British West Country used his chicken manure to produce methane with which he ran his car.

John Anderson,
Shipley, UK

What is the origin of the term 'Left-wing' or 'Right-wing'?

. The use of the word 'wing' is a journalistic addition and we can ignore it. The terms 'left' and 'right' derive from the fact that, in the British Parliament, the Government sits on the right hand side of the Speaker and the Opposition on the Left. The British Government was traditionally seen as supporting the British establishment; therefore pro-establishment views were associated with 'being on the right'. Conversely, anti-establishment views were associated with being 'on the left'. In time, the term 'left' thereby became increasingly associated with socialist thinking and vice versa. The 'Mother of Parliaments' spread the use of the terms throughout the world.

Francis Boyle,
Yelverton, UK

Is it true that unleaded petrol is less efficient and therefore worse for the environment than leaded in terms of the amount of carbon monoxide and sulphur dioxide produced?

Melvin Wailer,
Luton, UK

Why is it inadvisable - or dangerous - to allow victims of electrical
torture to take fluids until many hours after the ordeal?

M Morgans,
Preston, UK

 

What were the origins of the Geneva Convention?

B Hastings,
Rugby, UK

Who was the world's longest surviving dictator?

Paul Wells,
Truro, UK