Wild cole plants (in the mustard plant family, Cruciferae) grow around the Atlantic and Mediterranean coasts of Europe. I am not at all sure however that this is the origin of the brassicas we grow today, despite what the books say.
Just a thought, offered in ignorance! Looking at the indo-european languages - the Greeks had "kaulos", the Romans "caulis"; the Anglo-Saxons "cawel", which became English "cole", German "kohl", and Scots "kail". And of course, we have today the "collards" of the southern USA, broccoli, "cauli"-flower, kohl rabi, and kale itself.
I wonder if the various indo-european migrations out of Eastern Turkey also brought us the brassica family - in the same way they brought the wheel, wheat, the horse, the cow, the sheep, and of course most of our European languages. Oh, and garlic?
White and Red Cabbages, with their distinctively shaped round head, appear to have been developed around 1200, possibly in monastic gardens.
Cauliflower (with a single head) was bred in Italy in the 16th century, and spread through Europe.
A variety of broccoli is known to have been grown by the Romans, but this disappeared in Western Europe. Modern Broccoli has apparently only been known since the 18th century.
Brussels sprouts are the baby of the family - their recorded history starts in 1213, when sprouts were first included in market regulations.
Mustard was used by ancient civilisations in the south eastern Mediterranean for its oil, as a spice, and as a medicinal plant at least as far back as 2000 BCE. It was introduced to Western and Northern Europe in the Middle Ages.
Sad that such a long and noble history should be boiled to a colourless smelly sludge in countless school meals of memory!
It is however no surprise that there is now a bewildering range of varieties, for different seasons and climates. It's also interesting to let the odd brassica plant grow on into a second season - and see how a Spring Cabbage starts to look like a Brussels Sprout plant, or a Kale put out Broccoli-like flower heads; it gives the smallest of ideas about how people might have started selecting plants to reinforce certain aspects - flower heads, swollen stems, heads, shoots, etc.
And then there are all the "Oriental Greens", developed in China and Japan from native mustards; hardy, fast-growing - and many of them at their best in winter. Another huge area of vegetables worth exploring!