Final answer:
Anatomically modern Homo sapiens arrived in Australia approximately 40,000 years ago and reached North America around 16,000 to 13,000 years ago. The migration of Homo sapiens to the Americas occurred significantly later than migrations into Europe and Asia. The specific timing and routes of these migrations continue to be the subject of significant debate.
Step-by-step explanation:
By 40,000 years ago, modern humans had spread throughout Africa, Asia, Europe and Australia. It seems that they did not arrive in the Americas before 35,000 years ago, and perhaps not until around 16,000 to 13,000 years ago.
Some groups continued moving south through Malaysia, into Indonesia and beyond. In places like Papua New Guinea and Australia, there is evidence of settlements at least forty-five thousand years old. Others groups making their way into southwest Asia from northern Africa entered Europe around forty thousand years ago, moving either along the Mediterranean coast or by way of Turkey into the Danube valley. By twenty-five thousand years ago, Homo sapiens had reached Siberia and other parts of northern Asia. And approximately fifteen thousand years ago, some groups in Asia crossed into North America, eventually reaching the tip of South America and settling at various locations in between.
Controversies Surrounding the Peopling of the Americas
Current evidence points to the emergence of the genus Homo in Africa. From these beginnings, human populations began moving toward the global north, east, and south in migratory waves. Motivations for these migrations included animal movements, overcrowding and resource scarcity, and, likely, curiosity and adventure. The movement into the Western Hemisphere, into North and South America, occurred significantly later than migrations into Europe and Asia; how much later is a question of enormous controversy today. How did the first peoples make their way to the Americas? When did they first arrive, and how did they migrate within these vast continents? The available evidence is inconclusive, leaving us with one of the biggest enigmas in human evolution. While there is some debate on whether earlier human species migrated into the Americas, the evidence we have today points to members of the species Homo sapiens being the earliest humans to do so. At this point, there is no evidence of any earlier hominin species in either North or South America. The Western Hemisphere was wholly settled by migrants coming from other continents.
Ancestral humans like Homo erectus migrated out of Africa almost two million years ago and made their way around Asia, the Near East, and Europe. But so far, no solid evidence has placed them in the Americas. It was only with the rise of Homo sapiens that the populating of the Americas began. Exactly when this occurred is not clear, but it likely started around eighteen thousand years ago at the earliest. Within a few thousand years, modern humans had expanded in small numbers around North America, Central America, and South America. There they developed their own agricultural traditions, independent of those that emerged in the Near East, China, and Africa. They also established a range of unique cultural traditions and later a number of sophisticated civilizations characterized by refined religious practices, monumental architecture, large urban populations, and in some cases, writing systems.
Archeological evidence indicates that Homo sapiens began migrating out of eastern and southern Africa as early as 200,000 years ago. This expansion took early humans deeper south, west, and north as far as the Mediterranean Sea. Approximately 100,000 years ago, groups of Homo sapiens left the African continent and began a global migration that lasted for tens of thousands of years. After crossing the Sinai into southwest Asia, early migrants out of Africa likely followed the coasts of Asia, and by about seventy thousand years ago, they had made their way into India and China.
That massive global emigration was complete by about 40,000 years ago (with the exception of the Americas, which took until about 12,000 years ago). During an ice age, humans traveled overland on the Bering Land Bridge, a chunk of land that used to connect eastern Russia to Alaska, and arrived in the Americas. Later, very enterprising ancient humans built seagoing canoes and settled in many of the Pacific Islands. Thus, well before ancient humans had developed the essential technologies that are normally connotated with civilization, they had already accomplished transcontinental and transoceanic voyages and adapted to almost every climate on the planet.