Compared with our ancestor's diet, that consumed by present-day Western populations is higher in intake of energy, of protein (especially animal protein) and of fat (especially animal fat), but lower in intake of fibre-containing cereal foods; this diet is associated with high rates of morbidity and mortality from degenerative diseases. In the USA, the Dietary Goals report has recommended partial reversion to our ancestors' diet, including decreased intake of animal fat and protein, cholesterol, salt, sugar and alcohol--hopefully to reduce mortality from the six leading causes of death. 'Dietary goals', 'sensible eating' and the extreme 'longevity diet' are discussed. It is concluded that the general public will not voluntarily accept dietary changes of the magnitude required to promote a meaningful decrease in the burden of ill-health from degenerative diseases, because of: (i) conservativeness of dietary habits; and (ii) uncertainties about the extent of benefits likely to accrue. It is speculated, however, that in the distant future dietary changes of the type recommended will gradually but compulsorily be introduced, because of: (i) increases in population numbers; and (ii) the far greater economy of land usage linked with production of a near-vegetarian diet.