simalaraties between south india and africa

Not sure what you mean by "things". I take it you mean the animal species. I'm no expert but would guess the fact that the Indian sub-continent drifted from Africa as at least part of the reason.

If you are talking about people and culture, then the east coast of africa as far south as Madagascar have been trading with the, particularly south, indians for thousands of years. Not to mention the British moving thousands of Indian peoples to South and East africa to work on plantations only a century ago.

I think that there is a superficial resemblance which is the result of very similar environmental conditions. On the other hand, one should be careful about saying that they have a lot in common. For starters, both south India and especially Africa, have a very wide variety of cultures and languages. If one analyzes the respective social structures, religion, language, architecture and arts, one would probably notice enormous differences between South India and most of Africa. Most cultural similarities are likely the result of the two or even three millenia of trade between India and the East coast of Africa.

As do the scottish, the Amazon tribes and the Japanese: we all have similar genes. Unless there's a specific marker, that doesn't mean much.

 I find it interesting that you got the impression that I was racist, when in fact, I had the exact opposite intention. To elaborate, I think that a statement such as "many similar genes" is not very useful, unless we are talking about specific "marker" genes which are only encountered in certain populations (and there's not many of those). My remark was referring to the fact that as humans we all have similar genes: in fact there's more variation among a given population, than between the so-called races. So one could say that some from among the scottish, the Amazon tribes and the Japanese, the Dravidians and the Africans, they all share similar genes.

Africa and India were part of Gondwana, the Southern supercontinent:

There are some tribes in south india that are very similar to african tribes

Oh really, please elaborate on which specific tribes so that we can discuss the various differences and similarities.

I mean there are some tribes in America that are very similar to Aboriginees, they were forced onto reservations.