"The only species of palm cultivated by the South American Indians, that known as the Gulielma speciosa, has lost through that culture its original nut-like seed, and is dependent on the hands of its cultivators for its life. Alluding to the above-named plants Dr. Brinton ("Myths of the New World," p. 37) remarks, 'Several are sure to perish unless fostered by human care. What numberless ages does this suggest? How many centuries elapsed ere man thought of cultivating Indian corn? How many more ere it had spread over nearly a hundred degrees of latitude and lost all resemblance to its original form?' In the animal kingdom certain animals were domesticated by the aborigines from so remote a period that scarcely any of their species, as in the case of the lama of Peru, were to be found in a state of unrestrained freedom at the advent of the Spaniards." (Short's "North Americans of Antiquity," p. 11.) The most ancient remains of man found in Europe are distinguished by a flattening of the tibia; and this peculiarity is found to be present in an exaggerated form in some of the American mounds. This also points to a high antiquity. "None of the works, mounds, or enclosures are found on the lowest formed of the river terraces which mark the subsidence of the streams, and as there is no good reason why their builders should have avoided erecting them on that terrace while they raised them promiscuously on all the others, it follows, not unreasonably, that this terrace has been formed since the works were erected." (Baldwin's "Ancient America," p. 47.) We have given some illustrations showing the similarity between the works of the Mound Builders and those of the Stone and Bronze Age in Europe. (See pp. 251, 260, 261, 262, 265, 266, ante.) The Mound Builders retreated southward toward Mexico, and probably arrived there some time between A.D. 29 and A.D. 231, under the name of Nahuas. They called the region they left in the Mississippi Valley "Hue Hue Tlapalan"--the old, old red land--in allusion, probably, to the red-clay soil of part of the country.