Humans have been selecting maize for desirable characteristics ever since domestication of the crop Figure 1 (below) describes the traits of maize cobs found in four archaeological deposits from the Tehuacn cave in Puebla, Mexico. Rachis diameter refers to the diarneter of the cob at its base. Average number of rows refers to the number of rows of kernels per cob. A. Which archaeological layer contains the oldest maize remains? The youngest? B. Compare and contrast the oldest and youngest maize cobs in the archaeological C. Based on these data, what can you say about the kinds of traits that farmers have been selecting for in maize over the past 5,000 years? Figure 1. Corn cob fossils discovered in different layers of the Tehuacn cave inMexico. The age of each layer is indicated. Present- day corn consists of two differentvarieties. For each corn sample, theaverage rachis diameter and row number are noted. Modem Tatko Rachi damete kmd Aveage nunber of Moder A 1.09 Ae 000 Tabkono 09 Tabkoncie 17 Present Layer D M0 yan d 04 Layer C 472 ye 0.6 Modem Tabloncil Rachh diameter km) Average number of rows Moden Artoco Arrocillo 1.09 Arroclo &1 Present Tabloncle 0.9 Tabloncille 17 Layer D o yeen old 0.4 9.7 Layer C 4752 years eld 0.36 89 Layer B -5370 yean old 0.32 8.6 Layer A Ssao yen old 0.26 73