Knowing to which species one belongs is the easiest of all, as long before one's birth it's been decided that one will be born a pretty bird, annoying mosquito, a graceful wolf, cute monkey or just a boring old Homo Sapiens. This in itself doesn't mean much, however, as without anything else one is just a pile of cells taking up space. This is where instinct came in early in the evolution of life on this planet.
Instinct is the set of basic behaviourial rules any organism can or will use in its day-to-day existence. It allows one to find the right food, find a suitable mate, procreate and raise offspring. It also allows one to survive for as long as deemed necessary by the process of evolution.
Beyond pure instinct there is something else, something far more complex and interesting. It's what is commonly referred to as 'intelligence', defined as the ability to learn and reason. Many animals possess this trait to some extent, from a crow which will pick a lock by twisting a piece of metal wire into a suitable shape to a chimpanzee which will figure out how to solve the puzzle keeping it from retrieving a banana. It allows animals to use tools for finding and preparing food.
While it's debatable how smart animals like chimpanzees, bonobos, certain types of whales, elephants and others are, there's one advantage we humans have, namely that of having evolved appendages which can be used even more efficiently to manipulate our environment. While a crow can use its beak and claws to twist and move things, and a chimpanzee can grab a rock and use it to crack open a nut's hard shell, they can not display the kind of dexterity we humans can with our hands.
To be fair, humans are a pretty lousy animal. Our sense of sight is terrible, our sense of smell virtually absent, we can not survive colder environments due to the lack of fur, our skeleton is still half-way between that of an upright and four-legged creature and frankly, any half-decent predator will find a human to be an easy snack. It's a bloody miracle we survived this long.
What we humans are good at is manipulating using tools. The earliest humans, long before Homo Sapiens existed, already used stone and wooden tools, which changed from simple tools into complex weapons and devices including bows, spears, arrows, hammers and more. This led to the invention of such marvels as the wheel (except in the Americas, they didn't get the wheel until the Europeans dropped by), advanced shelters (houses) and allowed us to get by at the end of the ice age when the number of big prey suddenly dropped rapidly.
So from hunter-gatherers like pretty much every other animal we had to become farmers, manipulating our environment to sustain us instead of following the prey wherever it went. We invented farming tools, more advanced weapons to defend our farms, then farms turned into villages which turned into towns which became cities many hundreds of years later.
We learned how to construct more and more advanced houses, no longer using straw, wood and mud, but bricks and wooden planks. Houses which were more comfortable and lasted longer. At this point the wildlife was no threat to us any more. We had the means to defend ourselves and were safe in our cities behind the city walls. Next we had to face another problem: ourselves.
With a booming human population and rapidly overcrowding cities plus the firm establishment of 'countries' and smaller divisions therein, skirmishes and full out wars became commonplace, pretty much from the moment the first human settlements were formed up till this very day. While it may seem more rational to discuss the matter of resources like civilized humans, human history is a bloody one indeed with each war being more intensive with more casualties, culminating in the Second World War, still only just over 60 years ago.
It was human ingenuity which got us where we are today, yet it would be foolish to assume that this is an unavoidable process. I would like to draw parallels between certain aspects of human behaviour, instinctive behaviour among other animals and place the theory of 'devolving' as a background to this. Many things we humans consider to be typically 'human' are in fact not so human after all. Even insects wage war (ants, for example) with all the typical elements of conquering, surrender and various types of strategy present. Many animals are familiar with the concept of a mate (or mates) for life, which could be seen as 'love', or just an instinctive response with an apparently evolutionary benefit.
For the background of devolving I would like to use the movie 'Idiocracy' (2006) as an example. In this movie the two main characters find themselves in the future, five hundred years, to be precise. According to the theory of devolution as explained in the beginning of the movie, stupid people breed more offspring, offspring which itself isn't particularly intelligent and goes on to produce even more stupid offspring, whereas more intelligent individuals will postpone getting children or even decide not to have any children at all. This will then ensure that stupid individuals will become the majority, to eventually completely replace the intelligent individuals.
In 'Idiocracy' this is exactly what has happened in 500 years time. There's nobody left smart enough to keep most of the infrastructure running, entertainment has devolved into something as tasteful as cagefights, everybody drinks a Gatorade-like drink and even uses this to water crops with as 'it's got electrolytes' and 'plants crave it'. It is then up to the main characters to get some semblance of normality back into the world by for example using water to water crops with, even though water 'comes out of the toilet'. It's a movie which has to be watched to be appreciated and to draw all the parallels between its fictional world and the world of today.
What makes us human? Our intelligence, our knowledge and what we have done with it to improve all our lives. What doesn't make us human? Our instincts. Any time we surrender to these instincts, by eating lots of fatty junk food, leave school to pursue something 'more fun', enjoy purely carnal pleasures, use drugs and such stimulants, we give up our humanity. Whether one regains all of it afterwards then is the question.
As one of the main characters in Idiocracy put it, there can be a world in which being smart isn't weird. Being smart is good. Learning and understanding is good. Don't feel embarrassed to mention complex subjects or use big words in a discussion. It's okay to feel superior to those who feel that using slang instead of proper English and dressing like a monkey on drugs is okay. It's perfectly normal to feel disgust at the sight of someone with dark splotches of ink beneath his or her overly tanned or fat-covering skin, with or without of bits of metal embedded in various places.
We are human because we have superiour reasoning and tool manipulation skills compared to all other life on earth. We should be proud of this. We should be proud of being human. It's not a crime to be smart. It's what kept us as a species and the species we evolved from alive in the first place.
Be human. Be smart :)