A lot of comments are missing a basic fact of how science works. In science we have a theory, make predictions, then stress test them.
This is one study examining a theory which we have various lines of evidence for. It is not supposed to prove the theory - just test one prediction. It is not supposed to be the end of research on this topic. It is not supposed to be final. Criticizing it for any of those things is a demonstration that you do not understand how science is supposed to function.
This is one study examining a theory which we have various lines of evidence for. It is not supposed to prove the theory - just test one prediction. It is not supposed to be the end of research on this topic. It is not supposed to be final. Criticizing it for any of those things is a demonstration that you do not understand how science is supposed to function.
For some of the background on this particular theory I highly recommend reading https://www.psychologytoday.com/blog/evolution-the-self/2009... and the follow-up https://www.psychologytoday.com/blog/evolution-the-self/2009.... (If you want to get to the point, it is probably better to start with the follow-up.)