The Portuguese were the first Europeans to come in significant numbers to the archipelago. The golden age of Portuguese exploration and conquest in Asia began with Vasco da Gama's voyage to India in 1497-99 and continued through the first half of the sixteenth century. Faith and profit, nicely harmonized, motivated these early European explorers. The papacy charged Portugal with converting Asia to Christianity.

The Indian Ocean continued to serve as both a commercial and a cultural link between Indonesia and the countries to the west. Thus Islam, which was established on the Arabian Peninsula by the Prophet Muhammad in the seventh century A.D., followed the Hindu and Buddhist religions into the archipelago. By the late twentieth century, approximately 85 percent of Indonesia's inhabitants considered themselves to be Muslim.

Beginning in the 1890s, paleontologists discovered fossil remains of creatures on the island of Java that, while probably not the direct ancestors of modern humans, were closely related to them. These Javan hominids, known by scientists as Homo erectus, lived 500,000 years ago and some possibly as long as 1.7 million years ago. Their remains are identified as Jetis--the earlier specimens found in eastern Java--and Trinil--later specimens found in Central Java, including the Solo River area.

Before European intrusions into the islands by Portuguese, Spanish, and Dutch seeking to monopolize the lucrative trade in spices and other marketable products, the more than 13,000 islands constituting the Republic of Indonesia were home to a diverse array of cultures and civilizations that had been influenced by HinduBuddhist ideas from India and by Islam, as well as indigenous beliefs.