How populated was Australia by indigenous tribes at the time of first settlement?

Aboriginal Australians populated Australia at least 40,000 years ago.[http://ozzyremovals.com.au/ The Aboriginal Australians were semi-nomadic hunter-gatherers with a strong spiritual connection to the land, water, and animals. Each group developed skills for the area in which they would live, with significant diversity between groups.

In the early 1900s it was commonly believed that the Indigenous population of Australia was going to become extinct. The population shrunk from 1,250,000 in 1788 to 50,000 in 1930; this was due in part to an outbreak of diseases such as smallpox-

Current A.N.U. studies estimates that due to the huge numbers of language groups and very large permanent settlements that there were at least 2 million aboriginal people living in Australia when it was first landed upon by the British.

the aboriginals were nomads never stayed in one place therefore built nothing so who knows?

Australia had at that tme, over 500 different language groups spread over a vast area. I don't believe exact numbers of the population were ever recorded. Sadly it did not take long for the new arrivals to decimate the population and reduce those numbers hugely. I do know that in the region I live there were 4-5 different but related groups comprising about 5,000 people in 1860 but by 1880 that number was down to about 100 because of disease and slaughter.

Around 1 & 1/4 million. There were 3 main groups of people. Most were hit hard by small pox & other infermities when the British arrived.

Few hundred thousand backyard living people with customs that by today's standards are no longer acceptable. Predictably they sunk to a new level of depravity when civilisation arrived.

No one knows for certain but it is well known that most were wiped out by introduced diseases, apart from the genocidal actions of the very first settlers.

Prior to 1967 no records were maintained on the number of aboriginals in Australia. The 1967 referendum achieved 90% result by the people of Australia to have Aboriginal peoples counted as members of the Commonwealth.

1 too many

General estimates are about a million people in Australia when the First Fleet arrived in 1788. As Europeans spread across the country numbers fell dramatically to well under 100,000 over the next century. Numbers increased again during the 20th century but of the approximately 250 languages that existed 200 years ago, about 200 are now extinct.

I can't find any estimates, and I doubt that any were made at the time. The British established 2 settlements in 1787, and all the population statistics start there. I don't know how anyone could have determined the population at that time- the British were only on the east side until they found a passage over the Blue Mountains. In other words, indigenous people could have been living in places that weren't even seen for quite a long time. I found one estimate of 1,250,000 in 1788, shrinking to 50,000 in 1950, but this is an uncited statement on Wikipedia, so I don't know who came up with that number or how they got it.