They also constructed great mounds of earth upon which to erect their dwellings and temples. Like a good many of the other southern tribes, they fought when it was necessary, but they were peaceable compared with the Five Nations. They had a form of sun-worship resembling that of Mexico, and in other ways their ideas were like those of the people farther south. For instance, when a chief died, his wives were killed. In times of distress the parents frequently offered their children as sacrifice. Many characteristics of the Natchez and other southern tribes seem to indicate that they had formerly possessed a civilization higher than that which prevailed when the white man came. The Five Nations, on the contrary, apparently represent an energetic people who were on the upward path and who might have achieved great things if the whites had not interrupted them. The southern Indians resemble people whose best days were past, for the mounds which abound in the Gulf States appear to have been built chiefly in pre-Columbian days. Their objects of art, such as the remarkable wooden mortars found at Key Marco and the embossed copper plates found elsewhere in Florida, point to a highly developed artistic sense which was no longer in evidence at the coming of the white man. It is interesting to see the way in which climatic energy tended to give the Five Nations a marked superiority over the tribesmen of the South, while agriculture tended in the opposite direction. There has been much discussion as to the part played by agriculture among the primitive Americans, especially in the northeast. Corn, beans, and squashes were an important element in the diet of the Indians of the New England region, while farther south potatoes, sunflower seeds, and melons were also articles of food. The New England tribes knew enough about agriculture to use fish and shells for fertilizer. They had wooden mattocks and hoes made from the shoulder blades of deer, from tortoise shells, or from conch shells set in handles. They also had stone hoes and spades, while the women used short pickers or parers about a foot long and five inches wide. Seated on the ground they used these to break the upper part of the soil and to grub out weeds, grass, and old cornstalks. They had the regular custom of burning over an old patch each year and then replanting it. Sometimes they merely put the seeds in holes and sometimes they dug up and loosened the ground for each seed. Clearings they made by girdling the trees, that is, by cutting off the bark in a circle at the bottom and thus causing the tree to die. The brush they hacked or broke down and burned when it was dry enough.