Судлаачид 23,000 жилийн тэртээх хүний мөр болон хурдас давхаргыг шинжилснээр тухайн бүс нутгийн эртний байгаль орчны хувьслыг сэргээн тогтоов.
Нью-Мексикогийн “White Sands” үндэсний хүрээлэнгээс олдсон 23,500-21,700 жилийн тэртээх хүний мөрүүд нь тухайн үед уг газар нутаг хэрхэн өөрчлөгдсөнийг харуулж байна. Тухайн үед одоогийн хуурай цөлийн оронд “Отеро” хэмээх аварга том нуур оршиж, эргэн тойрны уулсыг шилмүүст ой бүрхэн, агаарын хэм одоогийнхоос 4°C-аар хүйтэн байжээ. Science Advances сэтгүүлд нийтлэгдсэн судалгаагаар эрдэмтэд 20 гаруй тунамал чулуулгийн давхарга дахь хүний мөр, амьтны ул мөр болон ургамлын үлдэгдлийг нүүрстөрөгчийн аргаар он цагийг нь тогтоон, ландшафтын өөрчлөлтийг нарийвчлан судалсан байна.
Дэлхийн уур амьсгал дулаарч, мөстлөгийн үе төгсгөл болох үед нуурын ус ууршиж, ой мод сийрэгжин, царс болон шарилж ургамал тархаж эхэлжээ. Судлаач Мэтью Беннетт болон Салли Рэйнолдс нарын тайлбарласнаар, хүмүүс байгаль орчны эдгээр эрс өөрчлөлтийн үед нуурын эрэг дагуу удаа дараа ирж байсныг чулуулгийн давхарга дахь мөрүүд гэрчилж байна. Энэхүү мэдээлэл нь Хойд Америкийн эртний хүмүүс мөстлөгийн хамгийн хүйтэн үед хүрээлэн буй орчны томоохон өөрчлөлтүүдийг хэрхэн даван туулсныг нотлох чухал баримт болж байна.
Мөрүүдийн тархалт жигд бус байгаа нь хүмүүс тухайн газарт ирэх давтамжтай холбоотой эсэхийг тодруулахын тулд багийнхан компьютерын симуляци ашиглажээ. Үр дүнд нь, зөвхөн нуурын усны түвшин өөрчлөгдөж, шаварлаг хөрсөнд үлдсэн мөрүүд зохих нөхцөл бүрдэхэд дарагдан хадгалагдаж үлддэг болох нь тогтоогдсон. Энэхүү загварчлал нь геологийн бүртгэлд ажиглагдсан мөрүүдийн тархалттай нийцэж байгаа бөгөөд тухайн бүс нутгийн гидрологийн өөрчлөлт нь хүний ул мөрийг хадгалан үлдээхэд голлох нөлөө үзүүлснийг харуулж байна.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
About 23,000 years ago, a group of people crossed a muddy lakeshore in what is now New Mexico. Their footprints have survived to this day, and scientists say they tell a far bigger story, that of a vanishing lake, retreating forests, and a climate shifting around the people who lived there.
White Sands National Park is best known today for its endless waves of white gypsum dunes. Yet between 23,500 and 21,700 years ago, the scenery was almost unrecognizable. A vast lake spread across the basin, conifer forests blanketed the nearby mountains, and temperatures were far colder than they are now.
The research team first made headlines in 2021 after dating the ancient footprints found at the site. This time, they turned their attention to the sediments surrounding those tracks. By reading the geological layers, they have reconstructed how this landscape evolved even as the world around them changed.
A Lost World Before the Desert
According to a new study published in Science Advances, White Sands went through a major environmental transformation during the last ice age. Back then, Lake Otero stretched across much of the Tularosa Basin, with temperatures around 4°C (7.2°F) colder than today. Conifer forests covered the surrounding mountains, creating a landscape quite different from the dry basin visitors see now.
As temperatures rose, the lake’s water evaporated and its shoreline gradually retreated. Forests declined, while oak and sagebrush spread. Some changes were abrupt, including a major drought that coincided with rapid shifts recorded in Greenland ice cores, thousands of miles away.
To reconstruct this timeline, researchers examined 20 sediment layers containing human footprints, large animal tracks, and other preserved markings. By combining radiocarbon dating of conifer pollen with dates from aquatic plant seeds, they were able to map the lake’s disappearance and the environmental changes that came with it.
The Land Changed, but People Returned
One of the most interesting findings is that humans didn’t simply pass through White Sands once. Their footprints appear at different points in the geological record, showing that people visited the lakeshore repeatedly while the environment was changing. The earliest tracks appeared around a major climatic transition, while others were preserved as Lake Otero continued to shrink.
As researchers Matthew Bennett and Sally Reynolds explained in The Conversation, combining the footprints with environmental evidence allowed them to reconstruct the landscape through which these ancient people walked. Their findings describe a region where water levels fluctuated, vegetation changed, and periods of drought affected the surrounding basin.
“This well-dated and highly resolved paleoclimate record,” the authors wrote, “provides compelling evidence that humans in North America experienced marked environmental changes during the Last Glacial Maximum.”
Why Some Footprints Lasted Thousands of Years?
Some geological layers contain numerous footprints, while others preserve almost none. At first glance, this uneven distribution might suggest that people visited the area more frequently during certain periods. But researchers found that the conditions needed to preserve a footprint could make a major difference.
To investigate this, the team used agent-based computer simulations to recreate people moving around a lake with changing water levels.
“Our virtual world consisted of people moving around a fluctuating lake,” the team wrote. “When they crossed mud, they left footprints. Those footprints gradually disappeared unless changing water levels created the right conditions for them to be buried and preserved.”
The simulations produced irregular clusters of preserved footprints, particularly during periods of climatic and hydrological change. This pattern closely matched what scientists observed in the actual geological record.
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