No they don't necessarily have larger families. The Pakistanis in Canada don't necessarily have large families and the same is true for Australia, although I know of exceptions.
Do you also know that Balochistan and Kashmir have small populations compared to the rest of Pakistan? It's not like Pakistanis are programmed genetically to have larger families.
It's because their native land provides the sufficient vegetation; especially calories to grow their numbers with Balochistan & Kashmir being the exceptions because they are not very fertile.
Outside your denial, how do you propose a species can grow to such large numbers without a preceding food supply to sustain them and to grow their numbers?
What you're suggesting is biologically impossible. For example are you familiar with the Lynx-Hare cycle?
Lastly I didn't know these are 'random' Youtube videos that I get this info from. From Google scholar:
Also since you mention Australia here's a quote from an interview with Dr Tim Flannery:
Q:
But what is it about the Australian landscape that makes it so unsuitable for supporting a larger population ?
Flannery:
Well, Australia has by far the world's least fertile soils so that half is fertile and average as comparable soils overseas. It's just very old land. A very ancient landscape. The soils here are a fossil resource, they're millions of years old.
And its very, very difficult to make a living from it. And you can see that in Australia today where our agriculture is in crisis. I mean 70% of our soils are degraded. The annual input of agriculture into the overall Australian economy is relatively declining and mining is taking its place so what we're doing is moving from the sustainable use of a renewable resource into exploiting a non-renewable resource which is mining, in a hope of continuing this growth. And that trend should be worrying for people.
Q:
Why is it that you believe Australia, which has an area the same size as the United States, can't support a similar sort of population - hundreds of millions ?
Flannery:
Really because the ecology of Australia is so different and so unique. Land size really has very little to do with the number of people you can support on it. Witness the Antarctic which is larger than Australia, and no one's suggesting in could even support a million people. The tiny island of Java which is very, very rich and fertile can support a hundred million. But Australia's ecology is very, very limiting.
So stop bringing up this "random YouTube videos" rant. The videos are well researched and not random. If you want to argue with a scientist like Flannery over this, then be my guest.