It is rather simple question:
Asian countries like China and India have huge population of people crowded in relatively small territory.
Whole Europe (including Russia) has about 700 million people, but much more high-quality arable land. Historically, Europe had the best conditions for agriculture, so why does Asia have much more people?
I can think of few explanations:
1) Civilizations started there sooner than in Europe (why? maybe the good natural conditions don't stimulate people to advance to next level? Does worse conditions (like in Mezopotamia, Egypt, Chinese plain, Indus and Ganges river valleys, Persia, Greece etc.)
2) Centralized government(s) are better in organizing large-scale agriculture projects (irrigation, canals etc.).
3) Culture more supportive of large families?
What do you think?
Actually, you've got your facts a bit off. India herself has enough good-quality agricultural land to support the entire world more than once over.
The British all but destroyed the agricultural prosperity of India, and that is why you think that Europe has better land. Famine was a work unknown to Indians before they came.
If you read the ArthaShastra, you'll realise why India has
always had a much higher population and population density that Europe, or in fact, anywhere else in the world. The agricultural, economic, and political institutions which that economic treatise describes are ones which can support vast and great civilisations, far denser than Europe and the West.
And it was written at a time when the land was not even fully tamed! Tax breaks for people or villages who build public works (like irrigation and roads), who bring barren land into cultivation, and stuff like that encouraged the building of a very intense and advanced system of agriculture.
However, governance was decentralised - the implementation of economic principles laid out in these treatises was left to the ruler, with advice provided as to how to keep the people happy and prosperous. Taxes were gentle - a flat tax of 16.67% of agricultural income. Customs duties were also not harsh. Women, the aged, learned men, and ascetics were provided with free ferry services by the state across rivers (these were the points where duties were collected). The sheer size and population density of India made centralised governance an impossibility.
There was something akin to a passport system - merchants and travellers had their papers stamped. Merchants had their goods accounted for.
The concept of the state acting as a buffer to stabilise the market for essential commodities was first proposed in India - Chanakya tells us that the ruler should buy grain at the time of an abundant harvest, when prices are low, and sell it when prices have, in his opinion, exceeded tolerable limits, to ensure market stability and to make sure that the poor can afford food. A side-benefit is that the state makes a tidy profit.
The wealth of those days is hard to imagine. The lowest salary a worker for the state could draw per year was five
panas, for part-time manual labour. The highest salary was sixty thousand
panas, granted to the ruler's inner circle. Five
panas was enough to sustain with dignity the manual labourer - imagine the wealth of the state when it could provide its top ranks with an income twelve thousand times larger - and then all the grades in between.
In general, the state of those times, before the Muslim invasion, resembled the modern state in innumerable ways. The ruler was always at the mercy of his subjects - "Keeping the people happy so that they do not revolt" is almost a mania with these authors.
Also, the Indus and Saraswati valleys provided an excellent ground for the building of a civilisation in India. If you see the climate of the region, and of Gangetic plain, you'll realise how much harsher Europe's climate is.
In fact, the effect of the twin invasions - by the Muslims, and by the British - have been so pernicious that the answer to such questions is not obvious. A thousand years back, these questions would never have arisen - the supremacy of Asia was an axiom, and the reasons for it were self-obvious.