Buddhism encourages people to get rid of certain negative qualities like anger, hatred, jealousy, selfishness.
But, considering an evolutionary perspective we couldn't completely tell what role they might be playing at a deeper level for the advancement of species as a whole even if they do appear bad on the first look.
So how can we be sure that a world without those negative qualities would be a better one.
I would not characterize them as "negative" as in arithmetic or electrics. Rather, they are conducive to suffering (by definition, i.e. being conducive to suffering is how these qualities are identified).
Suffering in Buddhism is an axiom, so it doesn't really have a definition — it's described by examples — but it is understood very broadly as anything that is phenomenologicaly experienced as not how one wants it to be, so the buddhist idea of suffering is not as much the physical pain as any psychological discontent whatsoever.
Whatever is conducive to suffering is considered unwholesome in Buddhism because — hey! — Buddhism is all about liberation from suffering. I admit it's a bit tautological or axiomatic.
So here's your answer, Buddhism encourages people to get rid of whatever qualities that are conducive to suffering, because it postulates that the world with less suffering is a better world. This assumes you agree that suffering is undesirable. If you think the world needs more suffering, well, I guess then go ahead and be angry, selfish etc., it's up to you. (There's no concept of sin in Buddhism, you are free to do what you like but there'll be consequences.)
Another doubt you may have, how does Buddhism determine which qualities are conducive to suffering, indeed, what if they're not. What if the Buddha was mistaken. Well, for one, Buddhism being a religion, we kind of tend to accept as the axiom that the Buddha was not mistaken, that he was in fact Enlightened.
A deeper truth, is that certain qualities are conducive to suffering because they set in motion certain kinds of causal latencies that create predisposition for a future experience of suffering. It's the good old "what you sow is what you reap" principle, nothing supernatural.
For example, being angry not only creates direct unpleasant experience for the one you are angry at, it also tends to upset people and results in them holding a grudge, which may backfire when you need their help. It can also create a bad reputation, restricting your future options. Additionally, anger is what's known in Buddhism as a "blinding affect" because it temporarily takes away one's ability to be rational, shaping the perfect conditions for violence, misjudgement, and other causes of future suffering. I hope I don't need to spell it out, at this point it should be clear: these causal chains and latencies constitute what Buddhism calls karma.
Now, is there something fundamental in the fabric of life that makes these qualities conducive to suffering? Is there some kind of natural law, or is it just some mysterious insight by the Buddha? Turns out, there's a law.
These qualities are conducive to suffering because the fundamental nature of suffering is contradiction between experience and expectation; and since 1) all experience is mediated by mind, 2) the nature of mind is representation, and 3) representation is not good at handling contradictions, it follows that unresolvable contradictions tend to generate the experience of suffering. To summarize, all activity that creates propensity for representational contradiction is conducive to suffering. What you sow is what you reap.
Now you can understand the Buddhist approach to liberation from suffering. It consists in methodically identifying and removing all behavior that creates propensity for future conflict, discord, contradiction - and therefore is conducive to suffering - starting from the coarser types and then refining, until no more suffering is left and one's experience is the perfect harmony.
I hope this answers your question in general. The Buddhist ethics and soteriology is more nuanced than what I can fit in one casual answer and does get more interesting as you "get in the weeds" so to speak, but this is the 40000 feet view.
To get back to your question, the way you framed the aggressive and egoistic traits as supporting the evolution with its survival of the fittest, may be a valid observation in the biological context, however I must remind you that Buddhism does not concern itself with evolution of species, its focus is the subjective experience of the sentient beings, namely cessation of current suffering and prevention of new suffering. From that perspective the evolutionary race, with its aggressive competition, dying out of losers, and procreation of winners, is exactly the cycle of samsara that keeps the sentient beings trapped and suffering.
From the evolutionary angle, cooperative behaviour is not without its rewards and benefits to an individual of a species as some scientific articles such as – Cooperation, Conflict, and the Evolution of Complex Animal Societies – indicated.
As effective cooperation in a society emerges, qualities such as altruism, empathy, conciliation and sociality become more evident. This, in turn, leads to complex social structure and interactions. Often, we see qualities that makes an individual’s evolutionary fitness high (i.e. more successful in spreading one’s genes) such as promiscuity tends to be less prevalent in cooperative societies.
This would suggest that getting rid of negative qualities would be good for society and the world. However, research had pointed out that cooperative behaviour can have an adverse effect on individuals. Similarly, we can see such adverse effects in human societies when individuals subject themselves to great self-sacrifices for the larger good. In companies with toxic cultures e.g. 996 work culture, such altruistic behaviour had resulted in health problems sometimes even deaths.
Likewise, qualities such as sociality has a dark side when they lead to collusions such as nepotism, cronyism and corruption. Such behaviours have detrimental effects on large segments of the society, creating social friction and even unrest.
So, what is the correct way forward? Negative and positive qualities appear to have their utilities depending on the context. Anger discourages wrongful behaviour by others. Hatred against harmful habits is a good thing. A bit of jealousy might spice up a relationship or push one to work harder. While selfishness can serve as a protective shield against unreasonable demands. Similarly, too much altruism may be harmful to an individual and encourage harmful qualities like dependency in the recipients.
The Buddha’s approach w.r.t what is better for ourselves and others (or the world) is to teach us to judge our actions using a simple yardstick. He advised that we ask ourselves the question before, while and after taking an action: Will this action leads to our long-lasting happiness and wellbeing?
When I first came across this teaching, it appears so simple. But over the years, I realized how difficult it actually is to implement. Firstly, it requires a lot of analysing, thinking and reflecting about the various factors, interactions within these factors and the likely consequences. The hardest part is that we live in a world that worships quick decision-making and fast executions. Time is money and speed is a competitive edge. If a person or a company take too long to deliberate on a course of action, they will lose the initiative and the first-mover advantage.
Our society just doesn’t afford anyone the time to think deeply into issues. The problems that we face today such as climate change, global warming and pollution in the air, land and sea are, in my opinion, the results of a culture that emphasizes getting whatever looks good out into the open ASAP. Even if there is a time machine to go back and change things. I doubt if we could convince countries/companies/individuals not to burn fossil fuels.
Just look at what’s trending in social media such as TikTok. I am sure some of these acts will look silly, if not stupid, decades from now. But if it catches attention and $$$, I am sure someone will start the trend. Similarly, in my IT career, this rush to push out projects in double quick time had come back to bite so many times that I had given up trying to make sense. In short, I think the ONE quality that is needed for a better world is that individuals, companies and societies take their time to think about important issues before acting.
The images of destruction due to violence in war-torn regions around the world are not very pretty.
In dependence upon craving there is pursuit; in dependence upon pursuit there is gain; in dependence upon gain there is decision-making; in dependence upon decision-making there is desire and lust; in dependence upon desire and lust there is attachment; in dependence upon attachment there is possessiveness; in dependence upon possessiveness there is stinginess; in dependence upon stinginess there is safeguarding; and because of safeguarding, various evil unwholesome phenomena originate—the taking up of clubs and weapons, conflicts, quarrels, and disputes, insulting speech, slander, and falsehoods.
Negative qualities like greed , lust , aversion , hatred , delusion are a result of craving. Craving results in clinging. Clinging results in attachments, attachments results in becoming, becoming results in birth , ageing and death , sorrow , lamentation, pain , distress, anxiety , diseases and the whole mass of suffering.
World without lust , hatred and delusion would be a great place as it will be free from suffering. But that is not how the world exactly functions. There is ignorance and ignorance spreads even more ignorance leading to volitional formations which lead to consciousness which leads six senses which leads to contact , which leads to feeling which leads to craving.
And as I have said craving leads to suffering.
