18,000 years ago, sea levels were 400 feet lower than today. The height of the last ice age is put at 24,500 BCE or 26,517 years ago. Glacial ice probably connected France with the northern British Isles. The south of England was arctic desert. Ice sheets covered parts of Finland, Norway and Sweden, but for the most part the ice age left northern Europe in permafrost, half of France and three quarters of Germany and Poland may have remained frozen year round.
Spain, Italy and Greece may have had a growing season still in the ice age. Cultivation may not have reached Greece and Italy until 10,000 years ago, coming across the Mediterranean from Egypt and the fertile crescent, i.e. the Tigris and Euphrates region of the northern Persian Gulf.
With lower sea levels, the Persian Gulf may have been cultivated, the earliest domesticated plants being fig trees, wheat, millet, flax, peas and barley. In the next thousand years humans domesticated gourds, rice, potatoes, and corn. Crop domestication came about first in the fertile crescent, but later crops like corn and potatoes came from as far away as South America, and did not reach Europe until the exploration of the 15th century, led by Spain and Portugal.