国产av不卡一区二区_欧美xxxx做受欧美_成年人看的毛片_亚洲第一天堂在线观看_亚洲午夜精品久久久中文影院av_8x8ⅹ国产精品一区二区二区_久久精品国产sm调教网站演员_亚洲av综合色区无码一二三区_成人免费激情视频_国产九九九视频

有名言說：“這世界上本沒有路，走的人多了，也就成了路。”不論是人類還是動物，都會在這個世界上留下自己的足跡。那么究竟是誰、在哪兒踏出了這世界上的“第一步”呢？

Scientists believe they have uncovered Earth's oldest known footprints in the mountains of Nevada（美國內華達州）—a fossil find that suggests animals have been walking around about 30 million years longer than previously thought, according to new research.

The controversial tracks—described by one skeptical scientist as "paired rows of dots"— may indicate animals had legs in the late Protozoic（原生動物的） era, about 570 million years ago, according to lead researcher Loren Babcock.

The discovery is the strongest evidence to suggest animals were able to move about on their own appendages during the Ediacaran period（埃迪卡拉紀）, before the Cambrian（寒武紀） period "explosion." During the Cambrian complex animals rapidly emerged and replaced simple multicellular（多細胞的） animals, said the Ohio State University professor.

About 570 million years ago, the area was covered by a shallow sea. The water had a mat-like surface made of sediment（沉淀物、沉積物） grains that were held together by a cohesive network of bacteria and fungi, which would have easily preserved animal tracks.

The tracks were determined to have been made in the Ediacaran period by comparing the "footprints" layer to previously dated layers with similar features.

（改編自：國家地理雜志 實習生瞿漫）

我要了解更多趣味百科知識