How advanced were the Neanderthals?

The Neanderthal braincase averages 1,640 cc for males and 1,460 cc for females, within the possible range of modern humans, which is, on average, 1,270 cm³ (78 cu in) for males and 1,130 cm³ (69 cu in) for females in present-day. For 28 modern human specimens from 190 to 25 thousand years ago, the average was about 1,478 cm³ (90.2 cu in) disregarding sex, and modern human brain size is suggested to have decreased since the Upper Palaeolithic. The largest Neanderthal brain, Amud 1, was calculated to be 1,736 cm³ (105.9 cu in), one of the largest ever recorded in hominids. Both Neanderthal and human infants measure about 400 cm³ (24 cu in).

Remains of Middle Palaeolithic stone tools on Greek islands indicate early seafaring by Neanderthals in the Ionian Sea possibly starting as far back as 200–150 thousand years ago. The oldest stone artefacts from Crete date to 130–107 thousand years ago, Cephalonia 125 thousand years ago, and Zakynthos 110–35 thousand years ago. The makers of these artefacts likely employed simple reed boats and made one-day crossings back and forth. Other Mediterranean islands with such remains include Sardinia, Melos, Alonnisos, and Naxos (although Naxos may have been connected to land), and it is possible they crossed the Strait of Gibraltar. If this interpretation is correct, Neanderthals’ ability to engineer boats and navigate through open waters would speak to their advanced cognitive and technical skills.