There is a sentence that is missing in the paragraph below. Look at the paragraph and decide in which blank (option 1, 2, 3, or 4) the following sentence would best fit.

Sentence: When people socially learn from each other, they often learn without understanding why what they're copying-the beliefs and behaviours and technologies and know-how-works.

Paragraph: _ (1) _. The dual-inheritance theory ....says....that inheritance is itself an evolutionary system. It has variation. What makes us a new kind of animal, and so different and successful as a species, is we rely heavily on social learning, to the point where socially acquired information is effectively a second line of inheritance, the first being our genes.... _ (2) _ . People tend to home in on who seems to be the smartest or most successful person around, as well as what everybody seems to be doing-the majority of people have something worth learning. _ (3) _. When you repeat this process over time, you can get, around the world, cultural packages-beliefs or behaviours or technology or other solutions-that are adapted to the local conditions. People have different psychologies, effectively. _ (4) _.