I've been looking for something to tell me the same thing for I was curious why one builds better over the other....Then I found that it's more so due to the amount of cortisol one particular body type produces over the other...ectos produce the most therefore making it more difficult to build muscle without outside help....Cortisol plays very important roles in health from what I found, ectos are less likely to get certain diseases such as heart disease, prostate cancer and others , due to the abilities to burn fat more rapidly and also maintain a more youthful look for a longer period of time....So though we struggle to gain the nice body size, we tend to live longer and healthier (this doesn't include those who smoke, drink heavily and all the other crap). Which makes since because there are many others my age and younger (ectos and mesos) that look 8 years older than me.....