石器时代-铜与锡的冶炼技术出现、私有制萌芽-青铜时代Bronze age（late Bronze age是prehistory和古代史的重要转折点）-铁器时代Age of iron（the glories of celtic warriors凯尔特战士的荣耀、druids德鲁伊教、kings、Romans、the building of towns、the introduction of writing）。

尽管说的也许都是网上有的，但其中折射的对历史的深刻思考，很有启发性。最后的一段话里还特意提及了历史责任感。

Ep4 ending talk

“It was as if we,as people,had come of age（成熟）.We had the keys to the door,（渐入佳境）,and we could mould the world in our own image（按照自己的蓝图塑造世界）as individuals,taking care of our families.But there is price to pay.That realisation,that thought,3000 or 4000 years ago,that we could impose our vision on the world,brought with it a very grown-up responsibility.Because what kind of world did we want to shape?What kind of Britain did we want to build?And we still living with the responsibility today.Because,in the great scheme of time,we're still busy trying to find ways to relate to one another.And we're going to pass the responsibility on to our descendants(子孙).And when they look back,what will they think?How will they remember us?