The Avic:
The Avic are catgirls; their appearance is at the Very Furry mark on this scale: [http://i.imgur.com/UGRGkXf.jpg]. They can have blonde, black, white, grey and brown coats.

Their physical capabilities (strength, speed, endurance, etc) have the same average and range as humans. On average, they are about a foot shorter than humans. Female Avic have (on average) smaller breasts than humans, but male Avic have larger penises than humans. By their own standards, all Avic are extremely beautiful.

Male and Female Avic have very similar builds; both have strong tendencies towards slim builds, with minimal visible muscle or fat. Excluding the presence or absence of breasts and genitals, they can be hard to tell apart.

Their children are born in just 1 month and take only 2 years to grow to adulthood. The first year takes them to the human equivalent of 16 years old; the second year takes them to the human equivalent of 18. They become capable of conceiving offspring around the end of the first year.

After this rapid growth, they have an average lifespan of 300 years. They are highly genetically flexable, suffering no ill effects from incestuous relationships. Avic are capable of having children with any other species that has offspring via sex; the resulting child is always an Avic.

Avic are simply born with innate knowledge of math, science, Avicis (their language), literacy and the "default" culture of the Avic. This knowledge comes in over the course of their first year. After this basic knowledge comes in, they have normal education to learn specialized trades.

It's worth noting the lack of history in this knowledge base. All of their knowledge of history is part of their follow-up education.

The Avic have a pair of "powers" that just don't fit anywhere else, if you will.

Avic can, at will, become infertile; once used, they remain infertile until they turn it back on. If two Avic have "proper" sex where they could concieve and neither have made themselve infertile, impregnation is all but guaranteed (99%).

When a Avic consumes alcohol, it does not have the normal effect. Anything more than a sip or two triggers a transformation; over the next hour, they transform into an opposite sex version of themselves.

The Avic are aware of both of these "powers"; they are part of their innate knowledge.

Now, onto their "default" culture. Their innate cultural knowledge draws them to this unless under the influence of another culture.

Before I get into it, I should point out that Avic value consent just as much as humans, if not more so (given the increased focus on sex as a whole).

Avic have no taboo against nudity; they wear clothes around humans for their sake, but when only around Avic, they only wear clothes for decoration or protection from extreme elements. They also have no taboo against public sexual activities, but don't do so very often for practical purposes; public spaces aren't designed for that.

For Avic, sex has almost no romantic baggage; it's connected a little bit, but not much. Sex is just a fun activity. It can help with bonding with a romantic partner, but it can also be done between a group of friends or even total strangers who are bored and have time to burn.

Avic tend towards bisexuality and polysexuality; it's rare to see an Avic who doesn't have multiple partners (unless they just don't have them yet). As such, they have no taboo against having multiple partners, even without telling the others; they have no concept of "cheating" in a relationship, sexual or romantic.

Transgender Avic basically don't exist; not that cases of "born in the wrong body" don't happen, it's just the solution is a sex change potion (booze). That said, gender fluidity is very common among Avic; about 20% of Avic regularly change sex.

Avic place the age of consent at 1 year old (the human equivalent of 16), as that is the earliest they are capable of having offspring of their own. When interacting with humans, they follow human convention.

The Avic version of marriage works much like the human version, but it is only connected to love. They also have no rules against polygamy, which is common. It is considered poor taste for a married Avic to have a romantic relationship with someone outside the marriage, at least without the consent of their other spouses. Sexual relationships outside the marriage are fine.

As it has no ill effects on them, Avic have no taboo against incest. That said, it's considered in poor taste to have sex with your children until someone else already has, even if they ask (and they often do).

Left to govern themselves, Avic naturally tend towards rule by committee, with an elected council trusted to set the laws and operate enforcement.

As for the history of the Avic, no one's quite sure. Looking at their genetic code makes it very clear that they were created by an intelligent actor, but no one knows who, when or why.