That's simply untrue. Suicide among the Greeks and Romans was at least prevalent enough to have laws written about it (see https://en.wikipedia.org/wiki/History

That's simply untrue. Suicide among the Greeks and Romans was at least prevalent enough to have laws written about it (see https://en.wikipedia.org/wiki/History_of_suicide https://en.wikipedia.org/wiki/History_of_suicide) and suicide among samurai was also certainly non-zero. If those examples are not "primitive" enough, already in 1894 Steinmetz collated an extensive list of at least forty-two documented cases of suicide amongst what he terms "savage peoples" like the "Polar peoples, North American Indians, Bedouins, Polynesians and native races of British India". Many of the terms he uses would be frowned upon today, but the article is available for free at https://www.jstor.org/stable/658295 https://www.jstor.org/stable/658295 and clearly documents many cases of suicide even in societies untouched by Western ideas. It's quite the list, from women killing themselves for "unrequited love" to adulterers committing suicide out of fear of repercussions. In fact he concludes that suicide may even be more prevalent in primitive cultures, relative to the size of the population, because some of those societies did not seem to have a stigma or taboo against suicide (unlike western civilizations where it is/was a sin).