A mutation could do that.
Codominance<span> is a relationship between two versions of a gene. Individuals receive one version of a gene, called an allele, from each parent. If the alleles are different, the dominant allele usually will be expressed, while the effect of the other allele, called recessive, is masked.
Credit: The internet </span>
possessing characters of both sexes and especially both male and female reproductive structures
hope this helps.
The calcium get into your body through Vitamin D.
<u>Explanation:</u>
In order to make the bones healthy, calcium and phosphorus is very essential. Calcium cannot be made by human body. The body only gets the calcium it needs, by means the food you eat, or from supplements. Vitamin D plays a major role in the absorption of calcium in human body. Calcium is a major mineral in a human body that helps in the proper working of body cells and nerves.
The quantity of the minerals like calcium, phosphorous,etc that are present in a segment of bone determines the density of bone. A percentage of 15 to 20 of calcium is absorbed from the diet that human intake. When the levels of vitamin D is low, there will be lower intake to calcium by gut. This causes the bones to become weaker.