Myostatin Knockout as Generally Beneficial Mutation
The existence of myostatin knockout mutations suggests that we should expect to find as many beneficial single gene mutations in humans are have been discovered in mice. There are at least one or two humans walking around with a naturally occurring version of this mutation. Here's more research into the benefits: "Humans and animals with a mutation in the myostatin gene are extremely muscular and have little fat, past research shows. Also, when the gene encoding myostatin is knocked out in mice, their muscle mass increases. ... The researchers took mice that were genetically altered to develop atherosclerosis and then cross-bred them with myostatin knockout mice. Ten generations later, they had mice who were genetically predisposed to both atherosclerosis and inactivation of myostatin. ... All mice received a high-fat diet for 12 weeks, to spur the development of atherosclerosis. ... the mice with deleted myostatin gene had much less body fat and 30 percent lower fasting blood sugar and 80% lower fasting insulin levels, showing a reduction in obesity and a strong resistance to developing diabetes, the authors reported. They also had 50 percent lower low-density-lipoprotein ("bad") cholesterol and 30 to 60 percent lower levels of total cholesterol and triglycerides (fats in the blood), respectively. These results indicate protection against the development of atherosclerosis."
Link: http://www.eurekalert.org/pub_releases/2009-06/tes-bam061009.php