Over the course of history the advancement of science and technology has been readily apparent. Of course there are setbacks and changes in the rate of advancement due to war and other circumstance, but is the same true for morals and ethics.
In prehistoric times perhaps the only people that mattered were your tribe or your family. But then with cities and nations people were bound to and cared for even larger grroups. Now more recently with globalization even national borders mean less and people recognize all humans as worthy of consideration.
In the United States we see equal rights and civil liberties being expanded to include more groups over time. At first only white men were equal in the law and then came women and then other races, and now transsexuals and homosexuals are more equal. Also internationally is there less dehumanization or polarization on the basis of national boundaries? Can we project or predict that at some point in the future more people, more groups, or even more species will be considered equal under the law and may have some of the same protections that in the past were only afforded to white men? Is this an actual historical trend or could it be argued that perhaps the ancient Greeks had treated more groups with equality than we do now and there is no progression towards advancement but more so just a gradual shifting around of in and out groups.
and there is no progression towards advancement
This is probably the most consistent statement with an anthropological position. First of all, "advancement" is never really defined in your question (or indeed, in most questions of this nature we receive on this sub), and that is the first thing that needs to be resolved.
In some ways it seems self-evident that some technologies are more "advanced" than others, e.g. guns vs. bows and arrows. However, what criteria are we using to make that determination? The obvious criteria is to look at the efficacy of each technology in accomplishing their primary end, which in both cases is wounding/killing. In that sense, we could argue that the gun is more "advanced". However, if we change our criteria of "advanced" to be based on say the ease with which a technology can be produced, the bow may in that sense be more "advanced" than a gun. Consider that an individual could fairly easily produce a functional bow for themselves, whereas it would be very impractical for any one person to produce a functioning gun. The gun then is a clunky, impractical device in comparison to the bow.
The whole point of this digression is to say that while it seems self-evident that we've made technological "progress", that is only true under a certain set of criteria that define "advancement" and "progress" as production of new technologies, rather than refinement of existing technologies or any number of other criteria. Now, that may very well be a valid or useful criteria to use for defining "advancement", but it is important to understand that is only one definition and that the self-evident statement of advancement that you lead with ("readily apparent", for instance) is not so clear-cut.
The same is true for "moral advancement". The sort of democratic, liberal inclusiveness you indicate as moral evolution is again just using one set of criteria for advancements in morality. Indeed, its not hard to find examples even in the recent past or in the present of societies and movements that value the exclusion of outgroups as a moral good, rather than valuing inclusiveness as a moral good. Fascism and Nazism come to mind immediately, but I'm sure you can think of a number of others.
Given all that, I would suggest that the proper historical/anthropological position to take is not one of technological and moral "advancement", but one of adaptation to particular social and environmental circumstances.
For instance, you note that "prehistoric" societies generally organize themselves based on kinship and family in fairly small "ingroups". I assume in this case that by "prehistoric societies" you mean forager or hunter-gather societies. There are a number of hierarchical or state societies that would count as "prehistoric" but which are not primarily organized around family and kinship. Many Native American societies, for instance.
All that said, we can interrogate why foraging societies might have a less inclusive idea of morality in terms of ingroups and outgroups. Largely, it has to do with the size of the society. When "society" as a unit only consists of a small number of individuals who are generally all related to each other through a variety of kinship ties (consanguinity and affinity, primarily), it is fairly easy to organize society primarily around those kinship groupings. Ingroup/outgroup dynamics can be resolved largely through existing kinship ties.
Now, if we look at a larger, more complex society, the situation changes to a degree. By complex, anthropologists generally use an analogy to evolutionary biology, in that an organism is more or less complex relative to other organisms on the basis of how many components it has. For instance, a gorilla is more complex than a bacterium given the greater numbers of cells, organs, and other components that make up the gorilla.
In the analogy to societies, a hunter-gatherer society would be relatively simple given that every individual performs the same social roles within the society, more or less. A large, state society, in contrast, would be more complex because there were be a larger number of components to the society. These complex societies are marked by a number of different social roles, such as blacksmiths, farmers, or kings. Complexity in a society might also be a product of the number of different cultural or social groupings within the society. A multi-lingual society, for instance, or a society with a number of artisans guilds or a developed caste system.
What then does this have to do with morality and ingroup/outgroup dynamics? Well, but virtue of the large number of moving parts within the society, a complex society needs to find additional ways to maintain group cohesion beyond just kinship and family. Conflict between different individuals and social units in a hunter-gatherer society can largely be resolved by deference to some sort of family or kinship structure. While that method can continue to play a role in conflict resolution and the maintenance of social order in complex societies, the increased number of social groups (and so the increasing plurality of interests in that society) dictates additional methods of social organization.
For example, any sort of social hierarchy can serve to maintain social cohesion (e.g. your stereotypical pyramidal structure, with elites at the head of the society and a variety of other roles organized in descending order below these elites). A system of laws, or communal social institutions like shared religions or holidays (and their attendant communal rituals), are other methods for maintaining social cohesion despite the increased complexity of a society.
Another option is to establish certain outgroups and work at excluding those groups in order to simplify an increasingly complex society. This is a strategy taken, for instance, by many right-wing nationalist movements in the 20th and 21st centuries. An alternative option is to promote an ideology of inclusiveness and establish social institutions that bolster that ideology. Rule of law and "protected classes" as legal concepts, for instance, help bolster that ideology of inclusivity and maintain social cohesion.
In conclusion, perhaps it is more appropriate from an anthropological and historical perspective to see the "moral advancement" that you note as a social response to an increasingly large and complex "society" (in both a global sense, and on the national scale), rather than something being driven on its own by some historical impetus towards moral "progress". Historically, then, we might see an overall trajectory towards this kind of moral ideology of inclusivity because the overall trajectory of the planet has been towards increasing social complexity. However, that doesn't mean this is necessarily "progress" or "advancement" as much as it is adaptation to new social realities.
In that sense, we could consider this more a moral "evolution" (in the sense of adaptive changes) rather than moral "progress". The notion of moral "progress" has at its core the idea that less advanced or progressive forms and technologies are inferior to newly developed forms that are "advanced" or "progressive". However, should the current trend towards increasingly complex and global society take a turn towards simpler social forms, likewise this moral "progress" might prove to be maladaptive or simply unnecessary. The anthropological and historical position is then that this "regressive" social order is in no way actually "regressive" as much as it just represents a solution to particular social realities, in the same way that "progressive" morality is adaptive to different social realities.
In summary, you might have the causation backwards. It isn't that there is some inherent historical drive towards moral "progress" or "advancement", but rather that the historical trajectory of human societies (towards more complex societies) has in turn necessitated the kinds of social institutions that you are identifying as "progressive" or "advanced", but also some that you might consider "regressive" such as the formation of exclusionary ideologies, such as Fascism or nationalism.
Apologies for the very long diatribe, but I hope that clarifies the anthropological and historical position on the idea of "progress", whether moral or technological. I can provide some further reading on social complexity and social cohesion if you are interested.