G-force
Mike and Zeron compete for the chance to ride in an F-16 fighter plane in 'Fit to Fly'.
Related programme
For the BBC THREE TV programme Lab Rats, biologist Mike Leahy and his buddy Zeron Gibson put themselves a range of bizarre experiments. Here, Mike - writing with Hilary McQueen - gets to grips with the numbers behind the man's part of the reproductive system.
THIS ARTICLE CONTAINS FRANK DISCUSSION OF SEXUAL AND REPRODUCTIVE SCIENCE
Animal facts
Ever thought about how humans compare with the rest of the animal kingdom when it comes to sperm production?
• We can produce between 40 million and 500 million sperm in a good ejaculation. A ram regularly releases 95 billion, which is approximately 1000 times more.
• A human male can usually manage sex up to three or four times a day. A lion can manage it seventy five times a day during the mating season.
• When a man ejaculates he generally produces between 2 and 5 millilitres of sperm (about the same volume as a large teaspoon would hold). A pig routinely manages one litre which is 200 times as much.
• Our sperm cells are microscopic - we cannot see them with the naked eye. On the other hand some diminutive fruit fly species produce sperm cells that are 20 times their total body length. Imagine how it would feel for a minute. It would be like a man producing a python about 40 metres long from their penis. Ouch!
• In a man's sperm sample something like 30 to 70 percent of our sperm cells are motile (that is, they move with purpose). In rats or mice all the sperm cells will be motile.
• Generally, testicle size goes up with body size, but did you know that chimps have huge gonads relative to their body size, whereas a gorilla's gonads are tiny. Apparently it's all down to lifestyle: chimpanzees are promiscuous, gorillas are not.
Sperm and lifestyle
In the programme Zeron looked after himself and increased his sperm count, while I lived like a slob and decreased mine. You don't need to be a rocket scientist to realise that if you are trying to become more fertile, looking after the tackle is important. Plenty of exercise - though not to exhaustion - and not too much junk food will help. Alcohol is a no-no - alcoholics are notorious for their low sperm counts. Also, don't fly too much - the radiation you're exposed to at high altitude reduces fertility.
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Content last updated: 24/08/2005
About our expert
Dr Hilary MacQueen is a Senior Lecturer in Health Studies at the Open University. In addition to teaching a wide range of topics, she has carried out research in several areas, including infectious disease, cancer and reproductive biology. Currently, she is working on the effects of dietary fat on health.
