True symbolic thought emerges before 430,000 BCE: The discovery in 2018 of Neanderthal art dating back to 68,000 years ago, proved symbolic thought in Neanderthals. It also indicates strongly that symbolic thought evolved in or before our common ancestor about 430,000 years ago. This must be true unless either they evolved it separately in an example of convergent evolution or we’re wrong about the art, meaning we’re wrong about our idea that humans were not in Spain until after that art. (see my Occam’s Razor article.) 

See Beyond the Brain: Reassessing Neanderthal Intelligence, for more information. Humans and Neanderthals had a common ancestor about 430,000 BCE (current estimates range from 430,000 to 450,000 BCE). Humans did not evolve from Neanderthals, but both are the current evolution of a common ancestor: Homo Heidelbergensis. After the split, Homo Sapiens and Neanderthals interbred up to and as recently as 29,000 BCE. Through DNA testing we can identify DNA that came from interbreeding with Neanderthals. They built shelters, wore clothes, used tools, and spoke. Neanderthal DNA in modern humans is the highest in East Asians, intermediate in Europeans, and lower in Southeast Asians.

• Class: Mammal; Genus: Homo; Diet: Omninivore
• Brain Size: 1,200 to 1,700 cm³ (humans=avg=1,350; 1,200 to 1,500 cm³)
• Brain to Body EQ: 4.5 to 5.5, but maybe 6.2, or even 7.9? (humans=7.4 to 7.8)
• Evolved in Europe, spread to Africa and the Middle East.
• Last known: 29,000 BCE in the mountains of Polar Ural, northeastern part of Komi, Russian Federation.