# Do genes play a role in the athleticism and shape of a person?

I am an Indian with a small thin stature with some deposition of fat around my belly.I was wondering if genes play a role in fat deposition in the body for Indian, Chinese, European or African people. Fat deposition may differ among all these people around the belly, thighs etc. These people also differ in their stamina and speed naturally.

For example here in India in the game of cricket there has been no fast bowler out of 1.2 billion people who can do fast bowling because it requires a lot of strength and stamina.Also on field athleticism is also very bad compared to Australian or South African players.I assume that may be its because of some cultural or genetic problem.

All these characteristics you observe (speed, ability to play cricket, belly size, height, etc…) are what what we call in biology a list of phenotypic traits. Basically, the phenotype is a characteristic of an organism that we can eventually measure or describe (physiological, behavioural, morphological, and life history are four common classes).

In a given population the phenotypic variance (the variance in height for example) can be expressed as the sum of the genetic variance (=the genetic variance underlying the phenotypic trait of interest), the environmental variance (=the environmental variance underlying the phenotypic trait of interest) and the variance due to the interactions between genes and environment (the variance due to the interaction that is underlying the phenotypic trait of interest).

Mathematically expressed it gives:

$$V_{phenotype} = V_{genetic}+V_{environment} + V_{gen X env}$$

Therefore, for each trait there is a given part of the variance that is explained by the environment and a given part that is explained by the genes. We might go a bit further and defined the concept of heritability (in the narrow sense, see wikipedia article for more info). The heritability (in the narrow sense) is the ratio of the phenotypic variance to the additive genetic variance. Mathematically expressed it gives:

$$h^2 = \frac{V_{additive}}{V_{phenotype}}$$

Each trait has it's given heritability. The heritability can be defined only for a trait in a population (which defines $$V_{genetic}$$) and its environment (which defines $$V_{environment}$$).

For example, the heritability of height in human is around 0.8 (non-peer reviewed source). Which means that 80% of the variance in height in the world-wide population is explained by the genetic variance. See this post for more info about the concept of heritability

In your question, you also used (before your question was re-edited!) the word fitness (also it is not really present in your question). The fitness is a very important concept in biology, it is the ability of an individual to survive and sire offsprings. Our phenotypic traits influence our ability to sire offsprings and therefore our genes influence our fitness. If the whole phenotypic variance is explained by the environmental variance only, then, even the the trait is under selection, there will be no change in allele frequency due to selection. Note: an allele is a gene variant. If eye color is a gene, brown eyes and blue eyes are alleles (to make it easy). This change in allele frequency is called a response $$R$$ to selection $$S$$. This link between selection, the response and the narrow sense heritability $$h^2$$ is given by:

$$R=S\cdot h^2$$

So to answer your question. Yes, part of the variance in height, belly size, cricket playing ability, etc… is genetically coded. As the fitness depends on phenotypic traits, Yes, the fitness is genetically coded (otherwise there would have no response to selection). Therefore we're not all equal to playing crickets!

DNA testing is a growing trend in athletics since 2016 to design training regimens by analyzing a range of 40 genes that encode for different physical traits (scroll down for a list of those genes here). The genes predict mitochondrial and muscle mutations which are good for speed and endurance.

We don't know which physical activities Indians are good at because some countries spend 4.5 million for every Olympic gold medal and India doesn't. They are perhaps better than Japan and worse than Jamaica.

Samoans are physically strong, and have 19% denser bones than caucasians. And they have been surviving maritime life in cold and food-deprived conditions for many centuries. India is the most food-abundant region on the planet, together with East Asia. Nepalese are good marathon runners.

There are two types of skeletal muscle fibers. Fast fibers, which use sugars for fuel and do not require oxygen, kick in for tasks that require maximum force and quick action, such as sprinting. Slow fibers, which employ oxygen-using (or aerobic) pathways, power activities that require endurance, such as long-distance running. A protein called alpha-actinin-3 is made mostly by fast fibers and is implicated in their capacity for rapid force generation. (science mag)

It has been speculated that variations in this gene evolved to accommodate the energy expenditure requirements of people in various parts of the world.(wiki)

https://www.thehindu.com/sport/cricket/indian-cricketers-undergoing-dnagenetic-fitness-test/article20321195.ece

https://www.sciencemag.org/news/2018/04/south-asians-are-descended-mix-farmers-herders-and-hunter-gatherers-ancient-dna-reveals

https://vdare.com/articles/indians-aren-t-that-intelligent-on-average

https://www.researchgate.net/figure/Anthropometric-data-for-European-and-South-Asian-men_fig15_49677710