Human Population

For most of human history the global population grew very slowly. It took until ~1800 to reach 1 billion. Then:

Year	World population
~10,000 BCE	~5 million
1 CE	~200 million
1800	1 billion
1927	2 billion
1974	4 billion
2022	8 billion

That's a doubling every ~50 years for the past century — classic EXPONENTIAL growth.

Why so fast?

• Better food (agricultural revolution, fertilisers, GM crops, mechanisation).
• Medicine (antibiotics, vaccines, surgery, clean water).
• Sanitation (sewers, soap, hand-washing).
• Public health (vaccination, maternal care).

The BIRTH rate didn't change much — what fell was the DEATH RATE, especially among children. Most of those new people survived to adulthood and had their own children.

Population growth is actually SLOWING:

• Global growth rate peaked at ~2.2% per year in the 1960s.
• It's now ~0.9% per year and falling.
• UN projection: world population peaks at ~10.4 billion around 2080, then declines.

Why the slowdown?

• Education for girls + women → marry later, have fewer children.
• Contraception widely available.
• Urbanisation → children are 'costly' rather than 'extra workers'.
• Lower infant mortality → no need to have many children to be sure some survive.
• Costs of housing and education in developed nations make large families impractical.

Some countries (Japan, Italy, South Korea, China) are already SHRINKING.

This pattern — DEATH rate falls, then BIRTH rate falls, population stabilises — is called the demographic transition.

Every extra person needs:

• ~2,500 kcal of food per day → more crops, more livestock, more pesticide.
• ~50-200 L of water per day → groundwater + rivers under pressure.
• Materials (concrete, steel, plastic) → mining, manufacturing, waste.
• Energy → mostly still from fossil fuels → CO₂ emissions.
• Land → for housing, farms, roads — driving habitat loss.

Population grows MULTIPLIED by per-capita consumption to give total impact. So a small population of high-consumers (e.g. wealthy nations) can have a higher total impact than a large population of low-consumers. The richest 10% of the world emit about half of all CO₂.

MYP criterion D: 'Should we reduce population growth?' A grade-7 answer doesn't shout 'yes' or 'no'. It distinguishes:

• COERCIVE measures (one-child policies, forced sterilisation) — ethically very problematic.
• ENABLING measures (educate girls, provide contraception, secure social safety nets) — these are the things that have actually reduced birth rates in countries that have done them.

It also weighs population AGAINST consumption. A modest birth-rate fall in wealthy nations would cut CO₂ more than a much larger fall in poor nations.