How many human beings on earth

We start at the very, very beginning—with just two people a minimalist approach! Although it is unlikely that humans descended from two people, this approach simplifies our estimation. One complicating factor is the pattern of population growth. Did it rise to some level and then fluctuate wildly in response to famines and changes in climate?

Or did it grow at a constant rate? We cannot know the answers to these questions, although paleontologists have produced a variety of theories. For the purposes of this exercise, we assumed a constant growth rate applied to each period up to modern times. Birth rates were set at 80 per 1, population annually through 1 C.

Rates then declined to below the 20s by the modern period see Table 1. This semi-scientific approach yields an estimate of about billion births since the dawn of modern humankind. Clearly, the period , B. If we were to challenge our conclusion at all, it might be that our method underestimates the number of births to some degree. The assumption of constant rather than highly fluctuating population growth in the earlier period may underestimate the average population size at the time.

When we adjusted the date of the first Homo sapiens on Earth from 50, B. But perhaps these two sets of estimates form some sort of boundary as to the possible highs and lows of this slippery issue.

As new archaeological discoveries are made and analyzed using increasingly innovative methods, expanding our understanding of human population history, we look forward to yet again tackling this ever-intriguing proposition! Toshiko Kaneda is a technical director, demographic research at PRB; Carl Haub is a former senior demographer at PRB and is also the author of the original version of this article in Project Details Date May 18, Carl Haub Demographer Emeritus.

We first made this estimate in and have updated periodically since then. TABLE 1. Life expectancy at birth averaged 10 years for most of human history.

The birth rate would have to be about 80 per just for the species to survive. Infant mortality in the early days of human life would be high, probably infant deaths per Children were probably economic liabilities in hunter-gatherer societies; this might have led to infanticide, which in turn would require a disproportionately high birth rate to maintain population growth.

But, in animals at least, then comes the crash — where the ratio of animals to resources becomes so skewed that a period of fierce competition for limited resources breaks out, and only the fittest survive. After the crash, populations tend to slowly recover, but never reach as high as they were during the first boom.

People started getting concerned in the s that the number of humans on the planet was increasing too fast, according to evolutionary biologist Ben Phillips of the University of Melbourne. Declining resources, climate change, and global extinction rates unprecedented in modern history all suggest we're in the later stage of the boom.

If Australians want to continue living as we do without making any changes, and as a planet we want to meet our footprint, then the number of humans Earth can sustain long term is around 1.

Alternatively, we'll have to find three more Earth-like planets to support us. Even if the global population stabilised today, the rate of consumption in wealthy nations is much higher than the world can sustain.

The good news is that the things we can do to reduce our footprints have a lot of other benefits too. As individuals, cutting down on meat, particularly red meat, can significantly reduce consumption of resources. And research shows that rehabilitating degraded habitats and increasing tree cover can have great restorative benefits to our environment.

But the biggest changes that need to be made are at a systemic level, and they need to be led by government and industry. We need cleaner transport and power-generation industries, and we need to transition to a circular economy, according to Ms Sloan. To do this, the onus of responsibility for single-use items needs to be put back onto producers. For instance, if a soft-drink company wants to sell their drink in a plastic container, they need to recoup that bottle after it's been used and ensure it is reused or recycled.

When it comes to population, the highest rates of growth tend to be in developing nations. Research shows that birth rates tend to decrease as women have more financial security. Improving living standards in developing countries can also improve resilience to climate change, she added. On current trend we are on track for a population of more than 11 billion people by the end of the century. We acknowledge Aboriginal and Torres Strait Islander peoples as the First Australians and Traditional Custodians of the lands where we live, learn, and work.

If he did the same thing today, his thumb would eclipse 7. A billion hectares of new trees could pause the climate-change clock. Silicon Valley billionaires are moving into luxurious doomsday bunkers.