No one knows for certain what happened, but it's a fair bet that it was not an accident.
没有人知道究竟发生了什么,但几乎可以肯定这并非意外。
The nomads who made these markings lived by hunting and fishing during the last Ice Age which began about 35,000 B.C.and ended about 10,000 B.C.
这些痕迹是游牧人留下的,他们生活在从公元前约35,000年到公元前10,000年的冰川期的末期,以狩猎、捕鱼为生。