Men's noses are 10% larger than women's because they need more oxygen to feed their muscles Experts found that the difference in size comes from the sexes' different builds and energy demands - man have more lean muscle mass Study also explains why Neanderthals had such big noses in comparison to modern humans - they had much more muscle mass Noses come in all shapes and sizes but men's tend to be larger - 10 per cent larger, in fact. The reasoning behind this was not fully understood but now scientists think they have solved the mystery - and it is because men need more oxygen than women. The research carried out by the University of Iowa found that the difference in size comes from the sexes' different builds and energy demands. Experts found that the difference in size comes from the sexes' different builds and energy demands - men have more lean muscle mass Males in general have more lean muscle mass, which requires more oxygen for muscle tissue growth and maintenance. The size differences become apparent around the age of 11, when men begin to grow more lean muscle mass and women grow more fat mass. Previous research has shown that, during puberty, around 95 per cent of body weight gain in males comes from fat-free mass, compared to 85 per cent in females. Scientists say the new study also explains why Neanderthals had such big noses in comparison to modern humans - they had much more muscle mass. Scientists found that male noses grow disproportionately larger than female noses at the beginning at puberty (pre-pubescent boy pictured top left, pre-pubescent girl pictured top right; same male pictured in adulthood on bottom left and same female pictured in adulthood, bottom right) Study lead author Doctor Nathan Holton, assistant professor at the University of Iowa College of Dentistry in the United States, looked at nose size and growth of 38 people of European descent. The research team took external and internal measurements at regular intervals. They found that boys and girls generally have the same nose size, from birth until around the age of 11. From that point onward, the size difference grew more pronounced. Doctor Holton said: 'This relationship has been discussed in the literature, but this is the first study to examine how the size of the nose relates to body size in males and females in a longitudinal study. Scientists believe that Neanderthals (reconstruction pictured) had big noses because they were very muscly We have shown that as body size increases in males and females during growth, males exhibit a disproportionate increase in nasal size. This follows the same pattern as energetic variables such as oxygenate consumption, basal metabolic rate and daily energy requirements during growth. Doctor Holton's research also explores why Neanderthals had bigger noses than modern humans. 'So, in humans, the nose can become small, because our bodies have smaller oxygen requirements than we see in archaic humans,' said Doctor Holton. This all tells us physiologically how modern humans have changed from their ancestors. Previous research also appears to support Dr Holton's findings. In a study published in the European Journal of Nutrition, researchers documented that men's energy needs are twice those of that of women's after puberty. Dr Holton also believes that his research, published in the American Journal of Physical Anthropology, helps us to understand the nose as a 'valuable extension of our lungs'. 'So, in that sense, we can think of it as being independent of the skull, and more closely tied with non-cranial aspects of anatomy,' he said. Even if the body size is the same, males have larger noses, because more of the body is made up of that expensive tissue. And, it's at puberty that these differences really take off.' Dr Holton says the findings should hold true for other populations, as differences in male and female physiology cut across cultures and races, although further research is needed.