Ancient Grains and Traditional Grains are two articles by Waldkorn, a Dutch company. These articles explain grain families and how modern grains were derived from ancient grains! For example, neither wheat nor corn (maize) are found in the wild. Both were created by humans through selective breeding.

1. Wheat: Wheat Domestication presents an overview of wheat history. About 11,000 years ago, we cultivated wheat from its ancestor: emmer. Luckily, emmer is still found today! Now emmer itself was derived from another ancient grain called 'einkorn' which is also found today.
2. Corn: Tracking the Ancestry of Corn Back 9,000 Years (NY Times, 2010) explains that corn (maize) was cultivated from its ancestor: a wild grass called 'teosinte', which does not look like corn at all! Teosinte is still found today — it is grown for fodder.

This article has a beautiful infographic tracing the history of wheat, barley, rice, millets and sorghum in Asia, Europe and Africa.

(Partial) List of ancient grains: einkorn, emmer, khorasan wheat, wild rye, fisser imperial barley, Baulander spelt.

Dr Greger has a video on this question!