While it may seem irrational, it's actually a trait that has been selected because people are fundamentally linked in societies as members of communities. A world that is uncertain, makes social connections even more important since people must rely on others in situations of threat or danger. Instinctively, people make choices driven by the connectedness of the species and the bigger picture potential for seeing someone again or needing help. Even if the particular circumstance doesn't lend itself to an ongoing relationship, the expectation of being part of a community drives people to give without the potential for future return.

Interestingly, generosity seems to be inborn as well. In a study by University of Washington, children as young as 19 months demonstrated sharing behavior, even when they were in need themselves. New studies show generosity is related to empathy. Those who take heroic action rushing into the ocean to save a drowning person or into a fire to save a stranger tend to have larger amygdalas and scientists believe they are experiencing greater empathy which motivates their split-second, high-risk actions.
Benefits of Generosity

In addition to being a deeply embedded characteristic which is correlated with happiness, and in addition to having obvious advantages for receivers of generous acts, giving also has significant benefits for givers.

Perhaps the best evidence of the social implications of giving, are the outcomes of a study by Ascent in which people who gave more generously reported they had greater numbers of close friends (3.2 friends compared with 2.6 friends for those less generous) and felt closer to their work colleagues (78% compared with 62%).
Being generous can also help you feel greater meaning. According to the Ascent study, acting more generously is also correlated with feeling more satisfied with life and career. Having a sense of meaning and satisfaction has to do with making a difference in something bigger than ourselves, and also connects to the feeling that we're making a positive contribution to those around us. Generosity pays off for these reasons.
Control is a factor as well. When so much feels out of control, choices about giving are very much within your control, and help you feel empowered How you think about others, to whom you give and how you provide for others through your time, talent or treasure offer opportunities to engage in the ways which are most meaningful to you.

How to Be More Generous

Globally, multiple communities report needs have increased across multiple groups with poverty on the rise and loneliness and mental health issues growing as well. Here's how you can be more generous and make an impact.
Think Broadly

In addition to money, you can give your time, your skills and your investments of energy. Packing lunches which are donated to food-insecure children or raking leaves for an elderly neighbor are perhaps more rewarding than just writing a check to your favorite charity. And volunteering is correlated with greater earnings and career advancement. Giving also has a positive ripple effect when you give, you gain greater awareness of your community, stay connected with friends and neighbors and even encourage others to give, because they experience your actions.
Think Small

You can make a big difference through small acts, small amounts of money or small investments of time. You don't have to commit to a weekly shift in a soup kitchen or a daily donation of fruit at the food pantry. The grocery store cashier who gave a few coins from her own pocket in order to round-up for a customer in dire need is a good example. In fact, the research on happiness from the University of Zurich found happiness was associated with generosity, even when acts were a one-time gift or a seemingly insignificant choice.
Think Empathetically

Sometimes people give based on what they love to buy or share, but it's a greater gift to provide what is most meaningful to those who are receiving. For example, rather than giving toys to families in need, consider giving laundry supplies so the families can spend their money on making choices of gifts for their children, rather than spending their money on mundane necessities.
Think Regularly

Notice, look and stay present in order to see opportunities regularly to make others' lives easier. Help the person on the airplane who can't reach the overhead luggage compartment, offer to help a colleague with a tough project or offer to take your elderly neighbor's returnable cans to the recycle center when you take your own.
Avoid Accounting

Being truly generous doesn't include keeping a ledger of what you've given and what you've received in return. In fact, you'll find more meaning in giving when you just give willingly without seeking returns or recompense.
In Sum

Ultimately, generosity is a demonstration of kindness, but also intention. It's keeping a lens on others and considering how to add value every day to others and to the community and in turn to yourself.