You're thinking of agriculture north of the tropics.

But there have been many societies which

- didn't engage in agriculture at all, or

- engaged in tropical horticulture, which is low-effort

And those societies (plains Indians / Australian aborigines / sub-Saharan Bantu (they're farmers! But they're not labor-intensive farmers) / central Asian Turks and Mongols / etc. etc. etc...) are characterized by near-constant warfare.

Not all societies are ancestral to yours. Most aren't.

Do you have any source to your claim that these societies required little work?

And seriously, claiming that a society will engage in warfare by comparing it to an example that is as remote to it as possible in terms of technological development and culture (we do view warfare as negative, not all societies do and ours used to not do so) is not exactly convincing.

That pre-colonial farming in Africa required relatively few hours of labor is well-known. I don't have a great link but "female farming system" is a term to start from (seriously, I didn't make it up).

The reason, if I understand right, was that the limit on human population was set by disease not labor. In northern climates (where fewer of the diseases we evolved with thrive) instead the marginal farmer was on some stony hillside from which maximum effort could only just produce enough calories for winter.

I'm less sure whether such societies were involved in more warfare, it's possible (the men had time on their hands & soccer hadn't been invented...) but I don't know the data.

I also don't know how to extrapolate this to the future of our society.