Prehistoric Wales in terms of human settlements covers the period from about 230,000 years ago, the date attributed to the earliest human remains found in what is now Wales, to the year AD 48 when the Roman army began a military campaign against one of the Welsh tribes. Traditionally, historians have believed that successive waves of immigrants brought different cultures into the area, largely replacing the previous inhabitants, with the last wave of immigrants being the Celts. However, studies of population genetics now suggest that this may not be true, and that immigration was on a smaller scale. Palaeolithic The earliest known human remains discovered in modern-day Wales date from 230,000 years ago. An early Neanderthal upper jaw fragment containing two teeth, whose owner probably lived during an interglacial period in the Lower Palaeolithic, was found in a cave in the River Elwy valley, at the Bontnewydd Palaeolithic site, near St Asaph (), Denbighshire. Excavations of the site between 1978 and 1995 revealed a further 17 teeth belonging to five individuals, a total of seven hand axes and some animal bones, some of which show signs of butchery. This site is the most north-westerly in Eurasia at which the remains of early hominids have been found, and is considered to be of international importance. Late Neanderthal hand axes were also found at Coygan Cave, Carmarthenshire and have been dated to between 60,000 and 35,000 years old. The Paviland limestone caves of the Gower Peninsula in south Wales are by far the richest source of Aurignacian material in Britain, including burins and scrapers dated to about 28,500 years ago. The first remains of modern humans, Homo sapiens sapiens, to be found in Wales was the famous Red Lady of Paviland, discovered in the 1820s. This was a human skeleton dyed in red ochre discovered in 1823 in one of the Paviland caves in Gower. Despite the name, the skeleton is actually that of a young man who lived about 29,000 years ago, coincident with a warmer period at the end of the Upper Paleolithic Period (Old Stone Age). He is considered to be the oldest known ceremonial burial in Western Europe. The skeleton was found along with fragments of small cylindrical ivory rods, fragments of ivory bracelets and seashells. Settlement in Wales was apparently intermittent, as periods of cooling and warming led to the ice sheets advancing and retreating. Wales appears