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When it comes to smarts, which is more important - nature or nurture, genetics or environment? Well, yes, it seems. New findings now suggest that half of all differences in intelligence between people appear rooted in the collective influence of many tiny genetic variations. That leaves plenty of influence open to other factors, the researchers said.
Past research had suggested that bright parents tend to have bright kids. However, the extent to which genetics contributes to intelligence, as opposed to other contributing factors such as environment, has been hotly debated.
No single gene variant has yet been identified as reliably linked with intelligence. Instead, scientists investigated the potential role of many common genetic variations on human intelligence.
A gene is a string of molecules known as nucleotides, much as a word is a sequence of letters. The recipe of nucleotides making up each gene is not always precise - for instance, the copy of a gene a person has might differ by one nucleotide from the copy of that same gene seen in someone else, much as the word "cat" differs from "car" by a single letter.
Comment: Exactly, "from the crater record" (that being the key phrase) there is no evidence for a Nemesis body. Clearly, the crater record is not the only evidence we have that comet encounters occur on a cyclical basis.
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