P.S.--By an odd coincidence, since the above was written I have received your very obliging letter of October 23rd. I did notice the point to which you refer, and will hereafter reflect more over it. I was indeed on the point of putting in a sentence to somewhat of the same effect in the new edition of the "Origin," in relation to the query--Why have not apes advanced in intellect as much as man? but I omitted it on account of the asserted prolonged infancy of the orang. I am also a little doubtful about the distinction between gregariousness and sociability.英文原著 · 《More Letters of Charles Darwin Volume I》
Generally he lives by himself, sometimes with his spouse, more rarely still with a third that is probably a grown-up son or daughter. I personally have never seen more than three in company. Some observers have reported larger bands, or rather collections, but, lacking other evidence, I should be inclined to suspect that some circumstances of food or water rather than a sense of gregariousness had attracted a number of individuals to one locality.英文原著 · 《The Land of Footprints》
This gregariousness and alarm at being left alone in a strange country tends to hold them together at night. You are reasonably certain that in the morning, having found one, you will come upon the rest not far away.英文原著 · 《The Mountains》