[3] This loss of CMAH is estimated to have occurred two to three million years ago, just before the emergence of the genus Homo.

[4] The latest research shows that humans who lack Neu5Ac on their red blood cells are less likely to get malaria from the parasites that cause it.

[citation needed] Neu5Gc is found in most mammals, with exceptions like humans, ferrets, the platypus, western dog breeds and New World monkeys.

[6] Trace amounts can be found in humans, even though the gene to encode for production of Neu5Gc was eliminated long ago.

Uptake is thought to be by macropinocytosis, and the sialic acid can be transferred to the cytosol by a sialin transporter.

Ingested Neu5Gc is incorporated into all body parts, some of which – mucins, hair, saliva, serum and blood – are commonly excreted.

[9][10][11][12] Sialic acids are negatively charged and hydrophilic, so they don't readily cross the hydrophobic regions of cellular membranes.