What do you think might be very different in our world if people only had one generation memories?

While the following quote is not from The Giver, it does apply to the book and this question. George Santayana once wrote the following:

Those who cannot remember the past are condemned to repeat it.

The Giver echoes this notion when he says to Jonas twice "They know nothing," and the Giver is filled with bitterness when he says this. He knows the past, and he knows the mistakes that have been made and the responses that were made to those mistakes. Unfortunately, the Giver is hardly ever asked to weigh in on things anymore, so he is seeing the same things repeated over and over again. The people know nothing of what came before them. The Sameness took away that ability; however, the people believe that they are happy. They believe this because they have no memory of the pain and suffering of anything in the past. They don't remember any happy things either, because the absence of pain is supposedly happiness.
It's hard to say if our current, real world would be similar to Jonas's world if we had no memory of the generations before us. It's possible that world peace happens, but it's also possible that the world ends in nuclear holocaust, because nobody can remember the destruction that was brought upon Japan at the end of World War II. I think for sure the sense of pride in a person's family line would cease to exist. Who your grandparents were and what they did wouldn't matter to people, because they can't remember it anyway. Schools might look completely different too. History classes likely wouldn't exist. Scientific knowledge might take a huge hit too, because so much of that knowledge is built upon the ideas and work of previous scientists.