Final answer:
Homo erectus appeared in the fossil record about 1.8 million years ago, and Homo ergaster is often considered a variant or the same species. Both are noted for more human-like features and technological advancements like the Acheulean tools. Homo erectus is considered the longest-surviving Homo species, with some Asian populations potentially existing until 25,000 years ago.
Step-by-step explanation:
Homo erectus appeared in the fossil record approximately 1.8 million years ago and is notable for being the first hominin to migrate out of Africa. This species, which had features more similar to modern humans than earlier species like H. habilis, was identified at sites across India, China, and Java, referred to by names such as 'Java Man' and 'Peking Man.' Homo ergaster, which is often debated to be the same species or an African variant of H. erectus, lived around the same time and shows less sexual dimorphism, suggesting a potential shift in social structures and mating systems. The Acheulean industry, observed with H. ergaster, produced more complex tools that are identified as appearing as far back as 1.6 million years ago. The longest-surviving species of the genus Homo, Homo erectus evolved for almost two million years and might have existed up to 50,000 years ago, with some sources indicating survival in parts of Asia until 300,000 or even 25,000 years ago.
Evidence suggests that by 1.75 million years ago, Homo ergaster may have begun a northward migration out of Africa into Eurasia. Analysis of fossils like KNM ER 1808 indicate an increase in meat consumption and perhaps an adaptation toward hunting. Their brain capacity and anatomical structures were more efficient for hunting and walking, and their use of fire had implications for cultural and technological development.