What are the implications of the theory that bananas arrived in Africa 5,000 yea

Listen to part of a lecture in an archeological class.
    Professor:
    So, those scientists in Uganda dug down to sediments that were 5,000 years old. And what do you think they found? Banana phytoliths! Obviously, this meant that we had to rethink our previous notions about when bananas first arrived in Africa. But, well, this discovery had other implications for history.
    As soon as bananas appear in the archeological record, we know we have contact between Africa and Southeast Asia. It would appear now that this contact occurred much earlier than previously thought.
    Al… although… now here’s where the uncertainty comes in… we don’t really have any solid evidence of trade between the peoples of these two regions that long ago. Presumably, if people were bringing bananas to Africa, they’d also be bringing other things too: pottery, tools… all sorts of objects made for trade or daily use. But such evidence is missing from the archeological record.
    The early appearance of bananas also suggests that agriculture began in this part of Africa earlier than scientists imagined. You see, bananas, at least the edible kind, can’t grow without human intervention. They have to be cultivated. People need to plant them and care for them. So, if bananas were present in Uganda 5,000 years ago, we would have to assume… that… that… that someone planted them.