These are photos representative of the two populations which are now very blended but would have once been very distinct. North Indians are Indo-Europeans (Aryans). South Indians are related to Melanesians and other very ancient populations. They created civilization in India/Pakistan. The Aryan invasion took place around 1500 BCE, about 2000 years later than their invasion of Europe and 1000 years earlier than their invasion of the Americas. The resulting hybrid was the Vedic culture.
Indo-European migrations map
Map of Indo-european migrations. Credit David Reich: https://www.hhmi.org/news/ancient-dna-offers-new-insights-origins-spread-languages-populations-across-southern-arc