You may not realise it to look at them, but the latest research suggests that men and women's bodies tick according to very different clocks.
A Canadian study has found that women have a circadian rhythm, which runs between 1.7 and 2.3 hours ahead of their male partners.
This means they are likely to feel more tired earlier in the evening than men, according to the study in the journal Proceedings of the National Academy of Sciences.
Such differences are mainly due to the influence of our sex hormones, says Dr Adam Taylor, a senior lecturer in anatomy at Lancaster University Medical School.
'These hormones can affect our health in everything from how fast our hair grows to how quickly we blink and even how rapidly we digest food and alcohol.'
Here, we look at some other ways in which men's and women's bodies run at very different speeds...
MEN DIGEST FOOD MORE QUICKLY
Food takes a fifth longer to pass through the digestive system of a woman compared to a man, according to gastroenterologists.
The reason is that women have smaller stomachs which produce less acid to break down meals.
Their slower rate of digestion is also linked to the female hormone oestrogen which seems to have a relaxing effect on the colon and bowel, according to a study by the American Clinical and Climatological Association.
Oestrogen also appears to change the composition of digestive bile, made by the gall bladder, so it contains fewer food-dissolving salts.
'The rate of movement through the gut is about 20 per cent slower in women than men,' says Dr Anton Emmanuel, a gastroenterologist at University College Hospital, London.
'The transit from mouth to emptying is about 24 hours on average in men and about 28 hours in women.'
As a result of this, women tend to have less frequent bowel movements than men, he adds.
A woman's heart is about two-thirds the size of a man's, weighing an average of 120g, compared to an average 180g in the male.
However, because the female organ is smaller, it beats slightly faster to make up for its size.
While the average male heart beats 70-72 times a minute, an adult woman's beats 78-82 times a minute.
However heart experts say this has no effect on women's overall heart health during their lifetimes or the type of heart problems they develop.
'It's probably down to numerous things such as body size, heart size and hormones,' says Miles Behan, a consultant cardiologist at Edinburgh Royal Infirmary.
WOMEN BLINK AT HIGHER RATE
Women tend to blink more often and more quickly than men — around 14.9 times a minute, compared to 14.5 times for men.
Again, it's thought to be due to women's higher levels of oestrogen — which stimulates the production of lubricants, including in the eyes.
Indeed, the blink rate of women who take high oestrogen birth control pills goes up to an average of 19.6 times a minute.
'It's possible that the contraceptive pills affect the lenticular nucleus, our brain's control centre for involuntary blinking,' explains Harminder Dua, a professor of ophthalmology at Nottingham University.
However, the difference in blink rates between the genders makes little difference to our overall eye health because women are still more likely to be affected by dry eyes, again for hormonal reasons.
Tears are made up of three layers — of mucus, water and oil, explains Glenn Carp, an eye surgeon at the London Vision Clinic.
'Men have more testosterone which holds these tears together better and keeps their eyes well moistened,' he says.
WOMEN GET DRUNK FASTER
There's a scientific reason why few women can drink their male counterparts under the table — they have less of the enzyme that breaks down alcohol before it enters the blood stream.
'Females have only about one-fifth as much alcohol dehydrogenase in their stomachs, so women get more effect, ounce for ounce, than men,' explains Dr Marianne Legato, founder of The Foundation for Gender Specific Medicine in New York.
It seems that as a result, women suffer more the next morning, too.
A survey by the University of Missouri found that women's experiences of the most common hangover complaints — dehydration, tiredness, headaches, nausea and vomiting — were more severe than men's.
This may have a long-term effect on women's health, says Dr Adam Taylor.
'A high amount of alcohol consumption in females has the potential to show a progression to liver damage more quickly than in men.
'This is probably because the female liver is having to do more work in the first place due to fewer enzymes being produced to process it.'
Women have to drink only half of what men consume — between seven to 13 drinks a week — to be at risk of alcohol-related liver disease, according to a 2013 study in the journal Gastroenterology and Hepatology.
MEN'S HAIR GROWS FASTER
On average, human hair grows about 1.25cm a month.
However men's locks grow fractionally quicker — about 6.5 per cent faster — than women's, according to a study published in the Journal of Investigative Dermatology.
This is because they have more of the male sex hormone testosterone, which stimulates the follicles to produce hair more quickly.
However, Iain Sallis, a trichologist who has a clinic at The Park Hospital, Nottingham, says it all evens out because testosterone also shortens the growth cycle of hair (how long each strand grows for before falling out).
Women, though, have the female sex hormone oestrogen in their bodies which lengthens the hair growth cycle.
This means that while women's hair does not grow as quickly, it grows for longer. In European women, hair has a growth cycle of around five to six years while men's is three to five years.
WOMEN SPEAK MORE QUICKLY
It's an old cliche that a woman is more likely to 'talk nineteen to the dozen', but there may be some truth in it.
Controversial research has found that women tend to speak faster than men, especially in social situations.
One possible reason is that oestrogen increases verbal fluency, while testosterone appears to dampen it.
Furthermore, the major areas of the brain related to speech in the prefrontal cortex — the part of the brain that governs social interaction — have been found to be 'significantly larger' in women by as much as 23 per cent, says a study in the Open Anatomy Journal.
According to a 2013 study, another factor is that females may have higher levels of a 'language protein' in their brains, called Foxp2.
In animal experiments, both male and female rat babies were found to call out more when they had higher levels of this protein.
The University of Maryland researchers also tested samples from ten boys and girls aged between three and five.
This showed the girls to have 30 per cent more of the Foxp2 protein than boys in brain areas key to language in humans.
Louann Brizendine, a neuropsychiatrist and author of The Female Brain, says: 'We know girls speak earlier and by the age of 20 months have double or triple the number of words in their vocabularies than boys.
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