Interesting Talk | Why haven’t humans formed a large number of fossils? Is it because human “skeletons” do not have the conditions to form?

I believe everyone has seen photos of fossils. Scientists say that it is not easy for organisms to form fossils. In nature, 99% of organisms will eventually become a piece of loess. The remaining 1%, even if decomposed by microorganisms, still has a very small probability of becoming fossils.

Some readers asked: Why don't humans form a large number of fossils? Is it because human skeletons are too small to form? In fact, humans do have fossils, such as Lucy, a girl found in Ethiopia in 1974. It's just that the number of human fossils is very small! In my opinion, there are three main reasons for the scarcity:

1. Humans have only been around for a short time, and have become globally distributed species for even shorter periods of time, less than 10,000 years.

2. The probability of terrestrial organisms forming fossils is much lower than that of aquatic organisms.

3. The probability of land animals forming fossils is much lower than that of plants

Reason 1: Fossils need enough time. Human history is only 2.6 million years old! During this period, only the earliest humans had the possibility of becoming fossils; the remaining ancient remains are just remains, far from being fossils.

Reason 2: The skeleton must be in an area of ​​continuous sedimentation, or washed into such an area by water flow. In this way, it will be below the sedimentary base level, covered by mud and sand, and gradually transformed into fossils.

Reason 3: This involves the necessary condition for the formation of sedimentary rocks - water. (Regarding sedimentary rocks, the editor has given a detailed overview in previous articles, so I won’t explain it here.) Therefore, when aquatic organisms die, they sink to the bottom of the water and begin to slowly bury them.

Over time, the remains of these creatures began to fossilize. As the Earth's crust moved, these underwater beds may have become mountain ranges; these mountains are where we find fossils today.

Reason 4: Plants grow stably and can reproduce in large numbers. If the geological environment here is suitable for the formation of fossils, a large number of plant fossils will be found. However, animals can move around and are not easy to find. If they are found, it can only be that during the geological survey, scientists happened to encounter that the stratum containing a large number of human fossils happened to be uplifted, which is extremely unlikely.

Here, the first point is time! The time required for fossil formation is probably longer than human history. The second point is the special place where fossils are formed - the base level of continuous sedimentation. So, here comes a point, what exactly is the sedimentary base level?

Let me explain: This is a virtual plane constructed by geologists. Weathering and erosion occur above the plane, and sediment accumulation (sedimentation) occurs below the plane. We generally use sea level as the standard sedimentary datum of the earth. On land, the planes of rivers and lakes can be regarded as the local sedimentary datum.

Therefore, geologists discovered that most of the earth is located in the ocean below the sedimentation surface, and a small part of the land is located in the lake below the local sedimentation surface. Therefore, weathering occurs on land, and sedimentation occurs in the ocean and lakes. At this point, some friends may still be confused, why are there more fossils in the water?

Below the sedimentary surface, sediments can be stacked and accumulated; and most of the sedimentary surface is located in the water, which happens to be the area where aquatic organisms live. Therefore, when a large number of aquatic organisms reproduce and die, a large number of biological hard bodies are continuously buried and accumulated by sediments layer by layer, eventually forming fossils.

This is what the editor said in reason 2: the probability of terrestrial organisms forming fossils is much lower than that of aquatic organisms. When the crustal plates move, the sea and the fields change, and the seabed in the past becomes a mountain range; with the weathering and erosion of the land, these precious ancient fossils were discovered by scientists.

Nowadays, when many people explain the movement of the earth's crust, they mainly focus on analyzing the plate tectonic theory of French geologist Le Picton and Wegener's plate drift theory; they directly skip the vertical movement of the earth's crust, which ignores the role of sedimentation.

As we all know, the surface of the earth is in a dynamic balance of "weathering-deposition" (so the sedimentation surface is also changing). In areas where subsidence occurs, the surface slowly drops and gradually becomes lower than the sedimentation surface; depressions form on the ground and become lakes.

In 1974, the mother of mankind, "Lucy", was first discovered in Ethiopia; this is a fossil of an ancient human of the species Australopithecus afarensis. After testing, Lucy lived about 3.2 million years ago, so she is considered the first human to walk upright.

So where exactly was Lucy found in Ethiopia? Geologists have the answer: Ethiopia's Afar Valley Floor - Hadar Location of the Awash Valley (Ethiopian section of the East African Great Rift Valley), located in one of the youngest geological settlements on Earth.

From the discovery of the mother of mankind above, it can be seen that the role of sedimentation cannot be ignored. In my opinion, sedimentation and fossils are inseparable for the following reasons:

1. When the ground settles, lakes will form. The water in the lakes flows, carrying a lot of sediment, which can bury biological remains layer by layer.

2. Lakes are conducive to the reproduction of aquatic organisms and the formation of fossils. Similarly, plants grow towards water, and the lake environment is conducive to the growth of shore plants and the formation of plant fossils.

3. Large-scale geological subsidence usually lasts for tens of millions of years. This kind of subsidence will put the animals and plants in the area in an environment that is easy to form fossils! In addition, the subsidence will form a stratum thousands of meters thick, which meets the formation conditions.

Therefore, paleontologists concluded that the remains of animals and plants living in non-settled areas are more susceptible to terrestrial weathering and erosion. Even if they are buried for a short period of time, once they encounter crustal movement, they can easily see the light of day and be weathered again.

I will translate this for you based on my own understanding: Most prehistoric humans lived in mountainous areas and hills, and their chances of becoming fossils are about the same as winning the first prize in the lottery. In addition, most of the land we live on is not a subsidence area, so it is extremely difficult to find human fossils.

This is why, in 2016, our archaeologists discovered late Homo sapiens fossils from the Peking Man period in Tianyuan Cave near Zhoukoudian, Beijing; this discovery was immediately awarded one of the top ten scientific advances in China in 2017 by the Ministry of Science and Technology.

From the above, we can find that caves have become an important burial site for early human fossils. Although caves exist on land, they are susceptible to weathering; however, compared to plains, the environment of caves is destined to be an excellent place for the accumulation of sediments.

What's more interesting is that geologists point out that the time between the birth of humans is only 2.6 million years. In 3 million years, weathering and erosion are not enough to destroy most caves! Therefore, these human fossils were preserved and discovered by archaeologists.

Today, we humans are active all over the world, climbing to the moon and catching turtles in the oceans, leaving our footprints everywhere. However, perhaps after tens of millions of years, we humans will disappear in the long river of history; perhaps we will become fossils, or perhaps there will be no evidence of our existence.

For example, we don’t even know how many species have existed since the birth of the earth? Humans are so insignificant in front of the earth; in the long river of time, everything will be wiped out, and humans can’t even create the slightest ripple! All we can do is develop technology to keep human civilization going!

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