I'm not an anthropologist, but I am an animal behavior student, and I can tell you that the man who coined the term "alpha" to deal with wolves later said he regretted it and wished he could take it back, because not only is it an inaccurate depiction of complex canine social behavior, it's been co-opted to completely inaccurately describe even more complex social behavior in humans.

"Alpha" implies first, as in first letter -- which, in wolf packs, is an accurate description of one social behavior, the "pecking order" or, in more scientific terms, priority resource access. The "alpha" eats first when a kill is made. However, studies of canine behavior over time have found that resource access order is not static. Wolves shift and jockey for access to resources over time and the "alpha" yesterday may not be "alpha" today, but may be again tomorrow. Animals are also now known to show empathy and altruism, offering first resource access at times to mothers, sick pack members, or their own children.

In human beings, the use of the term "alpha" is only really warranted where access to a resource is the matter in question. The only common situation I can think of where this is the case is where a same-sex group goes out intending to flirt with members of the opposite sex, and one member of the group has first priority in choosing among members of the opposite sex present in the venue. Even in this situation, however, there is more complexity than an "alpha" term implies. For instance, a recently single member of the group might be given priority resource access as part of a "bro code," with the most gregarious or attractive group member relegated to "wing(person)."

Overall, in human social groups, I would say that it's more effective to describe leadership as dominance over a realm of activity, rather than dominance within the group. For instance, imagine that there's a group of women who have been going out to lunch every Wednesday for 20 years. Susie is good at keeping an eye on new restaurants, so she usually chooses the place. Dana is a public speaker and manager in her work life, so she tends to speak first on behalf of the group when a waitperson addresses them. Leann prides herself on her etiquette, and the others in the group mimic her manners so as to be perceived as ladylike, like Leann. Tina is the biggest tipper, so at lunch spots where the group are "regulars," she gets the most extra attention from waitstaff.

Who is the alpha here? Susie has priority access to resources in that she directs the group to resources of her choosing. Dana has priority (first) access to the waiter, who brings food--but Tina has the most access to the waiter, overall. Yet, if you watch the group's interactions and judge them based on who moves first and is imitated by the others, Leann leads the way in body language. Each of these women could be described as the group's alpha, but in their everyday life, none of them is.