Yeah, for sure. That said, selfishness usually has pejorative connotations, so I'd probably unpack what it means to be selfish a bit. For example:
We have the type of selfishness that is an outward expression of what genes propel us toward. Look up self selection of replicators and good stuff like that. You can rootle around in kin selection models and all sorts of good stuff from evolutionary biology.
You could explore self interest from a more cognitive perspective. That would afford insights that old school biology alone can't really tap. It could transcend why a person might settle for a half used up woman or choose to share resources with a cuckoo's egg they have no relatedness to, and look at fun stuff like the perception of reward. One cannot meaningfully claim to know anything about altruism unless one has an understanding of what a reward can be, as altruism concerns behaving in ways without the perception of reward. If you perform a superficially selfless act that also ensures in your mind that you go to Valhalla, because your operating system has GOD V2.0 installed, then mebe that isn't a selfless as one might have uncritically thought. What of swerving being painted with a yellow stripe? Is swerving such a stripe selfish? We could go on. I don't think we need to here. It is sufficient to note that the concept of altruism and selfless behaviour degrades PDQ when you look at rewards. Note that avoiding averse stimuli is just as much a reward [selfish] as sharing food with that fat kid made me feel benevolent, I became a hero and a legend to people I would prefer thought of me that way, and Mother Teresa believing she'll get her hands on 72 virgins in some fantasy land. 'Till you can rule out what all possible perceptions of reward are there is no altruism. It's all selfish unless you are a nutter, because humans behave with reason and intent.
The last class is probably the one that is most salient as far as selfishness as something with negative connotations go because it concerns alliances and cheating. Self interested organisms can often behave in ways that maximizes the profits to each by behaving in cooperative ways. Hassles and aggravations can be overlooked because the sum of the rewards are bigger, and all the members of the collective benefit. Regardless of how sophisticated that is from; 1] can't think about it I'm a fish, 2] tacit agreement, 3] overtly stated [like marriage vows], it is all geared to the same ends. Membership within the group should return more sum profits that you would have had by not participating. On that, here concepts like pay-back, pay-forward, charity, Pro bono publico, you're putting yourself him harm's way cutting the bowbalds off the rapist doing something unspeakable to someone you don't give a shit about three roads away, can all be seen as selfish. You are supporting a system designed to bring you more rewards that you could access in isolation. But here's the crunch, there are cheats, and that is a selfishness with a completely different sort of loading. Defecting on your buddies with a middle of the night run to the turnip patch you are not entitled to is selfish too, but a bad kind of selfish because you have violated the rules of the game you agreed to because you benefitted from it. Enter green beards and grudgers, punishments and whatnot. Is it selfish of me to kick down morsels of food someone that can't hunt for themselves. Yeah if I'm plotting up on keeping a future babysitter alive. Different kind of selfish to I'm growing him up so one day I can defect on my husband with him.. though, innit.