why humans are selfish snd cruel?

The irony of your question, is that its also the answer for why many people are "selfish and cruel". It's because of the assumption that everyone is "selfish and cruel", which leads most to becoming just that. We're capable of kind, and giving, but its easier to be selfish, and taking.

Some will tell you it’s in our DNA.  Others will tell you because we fell out of grace with our creator.  But, what you really want to know is “Why is it okay for people to be cruel to me yet demand that I be kind and respectful to them?”

You could also ask, “Why was I born a peasant and not a King, Prince, or Princess?”

“.........Why am I the bug and not the wind sheild?”Not to put too fine a point on it, but not knowing the answer to that simple but monumental question is what makes you the bug and not the wind shield.  Those who have the answer are the architects of this reality.  They “need” you in order to support their illusions and work very hard to make sure that you never figure things out or escape your place of suffering.  

Humans are among the least "selfish and cruel" animals on the planet.

You're wrong, Violetrose. We are selfish because we, like all species, are programed to survive and reproduce. So self-preservation makes us selfish. However, most of the cruelty is a consequence of this instinct and is not practiced for cruelty's sake. In fact, we also have a "herding" instinct. That is we are a social group. Humans are basically defenseless. We have no fangs, claws, or horns with which to defend ourselves, but we found that in order to survive we could kill all other animals if we worked together. It's the same instinct other species have such as wolves. We are not naturally cruel. in fact there are thousands of examples when people from all over the world have come together to aid other people. Fukushima and 9/11 are two examples. Right now there are Americans in Australia fighting the fires there. People are moved to tears by the death of a small child or complete strangers who die tragically.....I could go on for paragraphs. So we are selfish in order to survive and we care for each other because we are all the same species. I won't live long enough to see it, but I hope some day we will recognize that we are all related and came from common ancestors. There is only one race and it's called human.

Not only human. Man hippo would kill baby hippo so that they can have the chance to mate with women hippo, these man hippo are so damn cruel and stupid.
As for the reason for human selfishness, there's a poetry in the book I'm reading that talks about it:

because many humans tend to only think about themselves. 

Not all humans, just those who haven't figured out some basic truths about life.

Their heart are dead ..... Look at Pakistan, they hate a selfish leader, but the biggest irony is that they are selfish themselves, use other people money, never give way at traffic, dont want to keep things clean unless it is their house .. Treat others cruelly ... They deserve such leaders

Because generations have to deal with the horrors of war and when it's finally done the next generation after the horrible atrocity gets the fruits and freedoms of the horrible atrocity that was suffered b4 them and doesn't quite understand what the incredible sacrifices were given and if aren't taught and showed it in it's horror is destined to repeat. 
Until we as humans make our young ever truly understand to the fullest extent the atrocities of being selfish and cruel will always bring, it will most likely never stop. Hasn't yet.

humans are selfish and cruel because others bully or hurt a person just to make themselfs feel good about themselfs. If somthing is happening to you than tell an adult or somone you trust so that they can help you.

All ,living creatures are selfish to a degree. This is necessary for surviv al. And some people are more so than others. I don't know how many times this blanket question has been asked on y/a. But there is no one answer.

The bottom line is survival. Kind or cruel, whichever aids in survival; At any given time.

If humans were created to reign over God's Domain, then we've just proven Spiderman's uncle, "With great power, comes great responsibility". The truth is a human power lust. Face it, some of us are givers and some are takers.
BTW, is all sex in the animal kingdom consensual? Do all animals have equal rights? Do animals choose their leaders?

Because they are the opposite of you

theyre not.................

We have a fallen nature inherited from our first parents Adam and Eve, when they committed original sin. All of us have been born sinners ever since.

Gov't is killing you with high frequency electricity.Theotokos Virgin Mary gave prayers to "Schema-nun Antonia" on how to save aborted babies from hell. If you pray these prayers diligently, aborted babies are released from hell. On each painted nail there are 40 demons. Smoking is censer to the devil.Using foul language calls upon Pagan deities (aka demons); Holy Spirit departs on 7 meters. People who use drugs see demons who cleverly disguise themselves as ghosts and aliens.America will be last country to switch to Euro (antichrist's world currency). Contraceptives = abortion;using contraceptives for 1 year = 5 aborted kids.Miscarriages happen because of high heels; cesarean because of tight pants (second generation cesarean will be infertile).Unbaptized aborted/miscarried/unborn babies burn in hell for until Final Judgement; if pregnant, keep the kid and deliver at home because kids are chipped using IVs and vaccines in hospitals. Dentists and doctors chip patients secretly. Ultrasound leads to mark of the beast; don't do ultrasound, please. Abortion leads to breast cancer; a demon is released from hell for each aborted kid. Dogs can become possessed; don't keep dogs inside your home [Pelageya of Ryazan]. Walmart has technology to administer mark of the beast to those who have cat bacteria in their stomachs; stay away from cats [Athanasius III of Constantinople]. Next false flag is the Statue of Liberty. Above earth there is ice (hemisphere); when rockets go up they bring ice down from upper sky to lower sky; ice stuck in lower sky will fall on us during Apocalypse. Earth is flat; earth stands on 3 pillars (the Most Holy Trinity); pillars stand on water at zero Kelvin; underneath this ice there is a bubble; and then the abyss. Zodiac is planetary prison of demons; don't believe in horoscopes or you'll exhibit the traits of the trapped demons. Most thoughts and dreams are from demons; demons never do good. Sleep fully clothed; pray the Jesus prayer. Pray to your guardian angel to have normal sleep. Vyacheslav Krasheninnikov was the last prophet before Apostle John (who wrote the Book of Revelation), Enoch, Elijah, resurrected Seraphim of Sarov, and resurrected Sergius of Radonezh will preach against the antichrist. Humans were created about 7525 years ago. Birds participate in time creation. It's a sin to kill birds. Dinosaurs live under our level; they will get out through sinkholes and lakes; to kill them, go for their nerves. Save the birds; but kill the dinosaurs. First dinosaur will come out of Volga River in Russia. Scientists don't see dinosaurs under our level because of radiation. Sinkholes happen because people dig for resources underground and because earth is heating up. Demons grow human skin (from a sample taken during abduction) and put it on so as to look like us. Demons will invite people to be healed inside their UFOs; those who go will be like zombies after. Gov't provides demons with diamonds and allows demons to abduct people. If you're being abducted, slowly pray the Jesus prayer. Don't panic. Demons use diamonds and souls to power their UFO craft. The bigger the diamond, the more it lasts. Demons have 4 UFO bases: 1)moon 2)inside fake mountain Kailash (Tibet) 3)in lake Baikal in Russia 4)in Atlantis which is underneath double ocean floor of Mariana Trench (Pacific Ocean). There are no aliens. Nobody lives on other planets. Airplanes that go down are hit by demons because they need the airspace to fight Jesus. Antichrist is pale with red eyes. He's possessed by Satan since he's 12 years old [Lavrentiy Chernigovskiy]. He flies super fast; deceived people will say: "Christ is here; Christ is there" when he's flying from one city to the next very fast. He wears gloves to hide long nails. He's surrounded by demons who appear as angels of light. Antichrist will trick people that he can do mountain moving and resurrection using holograms/hypnosis; fire from the sky is real because of pollution gases in the atmosphere. Antichrist will have food only for 6 months; then he will feed his 666ed people flour from mashed up turtles (Tavrion Batozskiy), but this won't be enough because 666ed people are 10 times as angry and 7 times as hungry as normal people even though 666ed people became shorter (3-4 feet tall = 80 - 120 cm) because nanochips do function of organs (organs diminish) [Nilus Myrrhgusher]. If you have a lot of nanochips in your forearm, then you will not be able to make proper Orthodox sign of the cross (last mercy for you will be to cut your forearm off). Nanochips are sprayed by the gov't using chemtrails; they're also in gov't food and medicine; so, eat food from your own garden. In case garden is destroyed by ice from the sky, have chickens for eggs and goats for milk (Paisios). Lipstick contains cells of aborted fetuses, dog fat, and placenta; human flesh is in McDonalds, Pepsi, toothpaste, antiaging, anticancer, vaccines, perfume, etc.; that's why you should not be using anything that modern society has to offer. You're better off hiding within a 10-12 people group in order to escape Apocalypse. During Apocalypse, Chrtistians will eat dirt from under pussywillowtree as it's filled with tears of Theotokos Virgin Mary; this water will flee if a 666ed person tries to get it. Barcode is Druid black magic curse; QRcode is Mayan curse; when food is scanned, it becomes dead because laser is a substance from demons. Don't go into a UFO to be healed by demons. Green 666 is given by isotope rays on wrist or forehead when people stretch hands to receive small plastic grey card with no name on it (World Passport). It doesn't just have to be during this procedure (could be anything you sign up for or anywhere where there is a secret scanner); biometrics (fingerprints, eyes scan) or getting picture for passport are very dangerous because they could mark you secretly. Gabriel Urgebadze said that they do it on index finger when they scan your finger. Basically, try to avoid new documents at all cost. Police will microchip and isotope ray people on highways. Chipped people will be influenced by computers to take grey plastic card; but when they do, green mark by isotope rays is given on forehead/wrist. Food stores will isotope ray people too. Antichrist will also release prisoners to mark people. Reject 666 at all cost because it leads to permanent hell. If you're about to be marked, pray the Jesus prayer. Hide with Orthodox Christians to escape 666; leave all electronics behind so that antichrist's minions can't track you; burn documents because they're from Satan. The Most Holy Trinity gives you a name during baptism; devil gives an antiname during antibaptism (ex. Social Security Number). People who die with these Satanic documents go to concentration camp in hell to await Final Judgement; once the BEAST Computer is burned down, souls will be released for Final Judgement. That's why you should give back documents of your deceased relatives back to the gov't so that the gov't cancels these digital antichristian names given during antibaptism by the beast system; or just burn these documents because gov't could get upset and could send demons to mark you because of this outright act of defiance. Prophecy from half a millennium ago describes Final Judgement like this: Jesus was very upset with people who had little boards (plastic cards) in their hands because they wanted discount from the antichrist. Give to charity in the name of Archangel Michael; he rescues people from temporary hell twice a year [at midnight September 18-19 and similarly on November 20-21; pray at these times on your knees remembering the deceased by names (adding "and relatives by flesh up to Adam") so that they are rescued if they're in hell] (or brings them up a level, that is, to a level with less punishment; eventually, people are freed). Feed the pigeons; when pigeons bow down, people are saved from temporary hell. It's a big sin to remember the dead with wreaths (because demons put these wreaths on their necks if they're in hell with their hands tied up behind their back while hanging by their hands), meat, alcohol, sweets, and worldly music. Demons print icons of saints in newspapers so that you throw these newspapers in the trash blaspheming these saints. Crosses on soles of shoes and back of pants are blasphemy. Demons make carpets with crosses and put them on sidewalks so that people walk on crosses. Playing cards mock how Jesus suffered on the cross: clubs (cross on which Jesus was crucified), diamonds (four nails Jesus was crucified with), hearts (sponge with vinegar that Jesus was given to drink),spades (spear with which Jesus was pierced).Cremation is devil worship; only blasphemers such as Lenin should be burned; if Lenin is buried, earth will be polluted, and China will attack Russia because of this.After China attacks Russia, Ruski Orthodox Tsar (shown by resurrected Seraphim of Sarov) will come to power in Russia;this Tsar will slay traitors inside church and gov't; as a result, Russia will be the only country not under the antichrist.Ecumenism = 263 heresies;each heresy leads to hell. In 2006 in Moscow (that's why Moscow will sink),representatives from most religions signed a document where it says that all religions worship the same Supreme Being [aka the devil]. Priests who participate in ecumenism will have Pagans walking on their heads in hell. Arkhimandrite Antonin Kapustin left a prophecy that Church of All Russian Saints in Gorny Monastery, Ein Karem, Israel will be blessed by forerunner of antichrist; Patriarch Kirill of Russia and Mark of Berlin blessed this church in 2007. When priests pray for current gov't (instead of praying for future Tsar),Jesus gets up from His throne and turns His back to them. Forgive me.

Animals ARE for eating says the last post from 2 days ago.  Buwahahagh!  What a dumb troll.  Well, that poster is also for eating, by worms.  Yous gonna be a worm factory, boy!

Because your mom gae

it takes all sorts...……..
the good can kill the selfish and cruel.
oh yes

Because I only care about myself

Speak for yourself. Plastic bags blow out of landfills 
and also trash cans that they are placed in, and are 
carried by the wind for miles, and read Genesis 9:3. 
Animals ARE for eating.

its human nature and DNA  and made by choices and events in humans life  all humans are not cruel or selfish its mainly the evil peolpe like that its part of light and dark light and dark been around since the beging of time since  the forbbiden fruit was eaten by adam and eve

Are you asking for your race of folks?
You can't make a blanket statement about 6 billion souls

It's how we survived for thousands of years. The ones who weren't selfish didn't procreate.

Not all of us are. Many people are capable of displaying kindness but “The whole world is lying in the power of the wicked one,” declared the apostle John. (1 John 5:19) Like its ruler, the world today manifests evil traits that include selfishness and pride. No wonder it is full of harshness and cruelty! But it will not always be that way.
Jehovah will see to it that kindness and compassion, rather than harshness and cruelty, prevail under his Kingdom.
Why not find out more.

Any two human characteristics you'd like to list are likely splayed on a bell curve (some to the left, some to the right, most in the middle).  What your question seems to be positing is:  humans are more selfish than altruistic, more cruel than merciful.  That implies that humans have a fallen or evolutionarily developed sin or cruel "bent."

As to why, generally two reasons are given:  mankind chose such behavior, even as idolatry in the Garden; mankind chose such behavior, as survival of the toughest, cruelest, most selfish.

Abraham Maslow did considerable thinking as to inner and outer self-actualization, which he termed higher, and the inner and outer self-aggrandizement, which he termed lower, and their complex interplay with inner and outer societal activities, which he also (for ease of analysis; these salients are all on bell curves ;)  characterized as higher and lower inner and outer socialization.

These are reflected in his research, that shows when people are more loving, capable, kind, self-actualizing, and in a social context, that the most optimal human development occurs:  https://en.wikipedia.org/wiki/Maslow's_hierarchy_of_needs

So an answer to your question:  the childish errors of selfishness, greed, fear, etc. are better therapeutically resolved by systems such as Dr. Maria Montessori's, which combines close attunement with the child, with freedom of the child to make choices, within a safe space (i.e., only appropriate penalties for real-world wrong choices).  When children of many places, typically of poorer urban families, were truly educated by such as Dr. Montessori, genuine miracles of development frequently occurred.  This indicates a terrific and horrific malstructuring of human society, and the continued sowing of such childish conditions.

To follow Confucius, rather than misguided totalitarian "philosophies" (e.g. marxism), is more harmonious:  nurture and champion your own inner psyche, soul, inner child--however you describe it--and then work with your family to share love, raise children in their Childlike lovingkindness, etc., explaining, teaching, and demonstrating why this is more desirable.

Related:

"Confucius from the Heart," Yu Dan;
"For Couples Only," Shaunti Feldhahn;
"Understanding Yourself," Mark Prophet;
"Youth:  Creators of the Future," Omraam Aivanhov.

Nature is cruel and only the self-interested survive.  Humans are a part of nature and all living things are all shaped by the constant competition for limited resources.  However humans can and do transcend this survival instinct and some are actually nice sometimes, even when they don't have to be.  Not all humans of course...

Well since erryone else is cruel we try to "out-cruel" them by being even more cruel.