What’s the meaning of ‘bursts’

The following passage is from the website as follows:

http://www.epubbud.com/read.php?g=H8AVF5J5&tocp=7

It was not that they were ‘primitive’ or that they had mentally regressed: it was that they had arrived with only a subset of technologies and did not have a dense enough population and therefore a large enough collective brain to develop them much further.
The ‘Tasmanian effect’ may also explain why technological progress had been so slow and erratic in Africa after 160,000 years ago. It explains the periodic bursts of modern tools found at South African sites like Pinnacle Point, Blombos Cave and Klasies River. Despite the invention of exchange, the continent was like a patchwork of virtual Tasmanias.

In this paragraph, I’m not sure what the underlined ‘the periodic bursts of modern tools’ means in the context.
It seems to me that it says modern tools have petered out at South African sites by context because of ‘Tasmanian effect’.

But when I think in terms of dictionary it seems quite different. it seems to mean “a lot of modern tools developed at South African sites, if I follow the example sentence of ‘a burt of anger’ in Oxford Dictionary.

Can you help me to figure out which is right?