Was the average person no better off in 1800 than in 100,000 BC? I was somewhat surprised by the following claims by Gregory Clark in A Farewell to Alms, A Brief Economic History of the World (2007):


  the average person in the world of 1800 was no better off than the
  average person of 100,000 BC. Indeed in 1800 the bulk of the world’s population was poorer than their remote ancestors. The lucky denizens of wealthy societies such as eighteenth-century England or the Netherlands managed a material lifestyle equivalent to that of the Stone Age. But the vast swath of humanity in East and South Asia, particularly in China and Japan, eked out a living under conditions probably significantly poorer than those of cavemen. ... for the majority of the English as late as 1813 conditions were no better than for their naked ancestors of the African savannah.


So, would most economic historians agree with the above claims? Or have any openly disagreed with the above claims?
In a detailed review of Clark's book, concluding that its "central theses ... are contradicted by well-known evidence" (p 969), Robert Allen addresses the claim about 1800 and 100,000 BC in a section headed "Malthus in the Very Long Run" (pp 951-5). His criticisms of Clark include:


That he has no evidence of living standards in 100,000 BC, but relies on an assumption that living standards at that time were the same as those of modern foragers (p 951).
That he draws inferences about diet (a key aspect of living standards) from male heights (from skeletons) but ignores evidence from female heights and from other skeletal features, which some have claimed to support different conclusions (p 952).
That his argument that humans of 100,000 BC had more leisure time (another aspect of living standards) because of their forager life-style is not supported by skeletal evidence comparing (more recent) foragers and agriculturalists (p 955).


Some other criticisms in this section are hard to summarise briefly. In conclusion of this section, Allen states: "Economic growth before the Industrial Revolution was not rapid, but it did generate a higher standard of living for most people than that enjoyed by ancient foragers".