North and Northeast Greenland Ice Discharge from Satellite Radar Interferometry
暂无分享,去创建一个
morphological changes that reflect an earlier automatic response on the part of the plants to the selective pressures of seedbed and harvesting (the adaptive syndrome of domestication) (1, 2, 17). The intact Cucur-bita seeds from the Archaic period occupations of the cave provide evidence, in terms of size increase, that such an adaptive response to seedbed selective pressures had occurred by ca. 9000 14 C years B.P. (ca. 10,000 calendar years B.P.) In the initial analysis of the Cucurbita assemblage from the cave (9), no clear morphological criteria were stated for assigning domesticated status to the Guilá Naquitz Cucurbita seeds, including the single seed recovered from zone D that was identified as domesticated. An increase in size above that documented for wild seeds has been the standard criterion for identifying the seeds of domesticated C. pepo 14 C years B.P.) seeds of a wild Cu-curbita gourd recently recovered from Amer-ican mastodon (Mammut americanum) dung deposits at the Page-Ladson site in Florida (12) provide a good wild baseline of comparison. The single seed from zone D of Guilá Naquitz has length and width dimensions (10 by 7 mm) that fall close to the average values (9.87 by 6.62 mm) of the Page-Ladson wild seed assemblage (range 8.73 to 11.15 mm and 5.07 to 7.60 mm), and thus it cannot be considered as evidence for the presence of domesticated C. pepo. Of the five measured seeds from zone C of Guilá Naquitz, four fall within or close to the upper end of the Page-Ladson size range in terms of length, although one has a length of 13.8 mm (Table 1 and Figs. 1 and 2C). The AMS 14 C date on this largest of the zone C seeds is 8910 14 C years B.P. (ca. 9900 calendar years B.P.) (Table 1 and Fig. 1). Seven of the eight zone B seeds also exceed the size range of the wild comparative baseline population (range 11.4 to 17.0 mm) (Fig. 1). Samples from five of these seven large zone B seeds have AMS 14 C ages of 7610 to 8990 14 C years B.P. (ca. 8400 to 10,000 calendar years B.P.) (Table 1 and Fig. 1). The largest and oldest of these dated zone B seeds was comparable in both size and age to the AMS-dated zone C seed. Taken together, these two seeds, both of which exhibit marginal ridge and hair characteristics diagnostic …
[1] R. Armstrong,et al. The Physics of Glaciers , 1981 .