An American biologist named E.O. Wilson said that the greatest mystery of life phenomena after taking all of these matters into consideration is "The most wonderful mystery of life may well be the means by which it created so much diversity from so little physical matter". There is no life that can live on its own. All life forms more or less live as an intertwined whole. So the surface of this Earth is filled with life. Life exists in every nook and corner with no ecological gaps in between. But when there is a forest fire like the one that occurred just recently and the entire forest is burned to ashes, a new space is created there as seeds germinate and new creatures arrive to start a new cycle.
To sum all this up. we must conclude that it is impossible to think about life without considering the entirety. In other words, we cannot think about life unless we look at the entire flow of time on vertical axis as a system and the entire biosphere as spatial expanse. Dr. Iwatsuki, who now teaches at the University of the Air, came up with a new word called "spherophylon". It is a combination of a word "biosphere", which represents the entirety of organisms from the viewpoint of space, and "phylon", which represents the entirety of organisms from the viewpoint of axis of time. All life is connected through time. He proposed this term "spherophylon" by combining the two. This term that he coined has been well-accepted in the rest of the world as well. In Japan, we call it "seimei-kei (life system)". Therefore, he is suggesting that we use the term "life system" when we refer to all life forms.
I assume that the ages of people that are with us today range from those in their twenties to those over eighty. Their age difference is about 60 years, but from the viewpoint of life system, this age difference of all of you here is totally irrelevant because all lives are 3.8 billion years old. To put it another way, plants and meats that we eat from day to day all come from our fellow creatures. All life originated from the same system.
As Dr. Matsui mentioned, we Homo sapiens have very unique characteristics. I may be preaching the converted here but one of such characteristics, as all of you here today know well, is the dramatic growth of population. As for the process of this population growth, farming started about 10,000 years ago. Population remained at extremely low level for a long time but started to increase rapidly after a certain point in time. When Buddha was born, the world population was less than 100 million. But it reached 3 billion in 1950. It has increased dramatically in the recent years, and, as all of you know, has already exceeded 6 billion today.
Number of an organism's population is bound to change. They never stay at the same level of population. But their number is almost constant in the long term. It is almost constant for all organisms. Needless to say, various things happen when some drastic change occurs but the population is immediately restored to a certain range. That happens when various organisms live and interact in a very complex manner.
However, human beings are the only exception to this rule. There was a talk about population quadrupling in the 100 year period of the 20th Century. Generally speaking, human race has been increasing by four-fold in 100 years, by ten-fold in 400 years, a hundred-fold in a little less than 3,000 years. In addition, it increased by a thousand-fold in 10,000 years. There is no other species like it.
Moreover, this rapid increase has occurred only over the last 10 generations. It increased considerably over a period of 10 generations. Dr. Matsui also talked about this but it is said that our ancestors and chimpanzee branched off about 5 million years ago. In terms of generations, 5 million years correspond to only 500,000 generations, assuming that takes 10 years to get offsprings for each generation. So we are newcomers to the world of organisms but have increased rapidly in number over a period of last 10 generations. And our population already exceeded 6 billion as a result.
I think you are also familiar with this fact but the number of people living on Earth today has exceeded 5 percent of the sum of population that has even existed since Homo sapiens came into this world. As I mentioned earlier, there are numerous varieties of life but the fact that several percent of the population that has existed since the origin of the species being alive today is a totally unprecedented phenomenon. We are truly exceptional in this sense.
I once calculated the weight of various species. Actually, we Homo sapiens are a very large animal. People often disagree when I say people are large. There are animals larger than us in reality, but a very large number of animals are so small that we need to use a microscope to see them. Some animals are larger but they are extremely limited. In the ocean there are whale sharks that are more than 10 metres long and whales that are even bigger. We also have elephants on land. But they are very limited. When you line up the species in order of the size of individuals, we fall under the category of very large animals. And the question is what would happen when there are 6 billion of these very large animals (Table 1).
Please take a look at the results of the weight of species. There are 6 billion people and if you assume their average weight to be 50 kilograms − it may be less than that in reality because people vary in size from babies to grown ups − total weight of humanity would roughly amount to 300 million tons. I said that there are very large animals when you take a look at all the animals that presently exist. Among them, whales, blue whales in particular, are the largest animal alive today. However, aggregate weight of blue whales is less than I percent of our weight because they are very few in number. African elephants are the largest animal on land but their aggregate weight is also insignificant compared to that of ours. You can understand how large our population is. A calculation of the aggregate weight of other species based on FAO's data from 1999 shows that cows are actually the heaviest and weigh about twice as much as people. They are followed by sheep, pigs and buffaloes among others. They are all livestock that are being raised by people for their own subsistence. So the large population of Homo sapiens is accompanied by enormous numbers of large mammals that are used for their activities.
|Table (1) Number of Species
|Name of species
||Weight (million tons)
The only non-livestock species heavier than us is Antarctic krill, on which whales feed on them. They look like shrimp and are seen in Japan on store shelves these days. About 500 million tons of them are born in some years. Like us Homo sapiens, antarctic krill exist as a single species and exceed us in aggregate weight in some years. They are the only exception.
I have done a lot of research myself but even the animals that are believed to exist in considerably large numbers are usually insignificant in terms of aggregate weight compared to us. It means that Homo sapiens and livestock exist in such large numbers compared to others.
Dr. Matsui talked about the path human species have treaded. It was on an issue of the Nature magazine that was published two years ago, but our ancestors started to spread out of Africa about 100,000 years ago and went all the way down to the tip of South America. Human habitation kept expanding to cover the entire Earth over a period of approximately 100,000 years. This is also very extraordinary. You may think 100,000 years is a long time; however, it is an instant from a geologic point of view. Such global spread by a very large animal is unprecedented and no other mammal has done this in the past. It is overwhelming just to think that all of our ancestors walked all the way from Africa, but, as Dr. Matsui mentioned earlier, it all became possible as a result of farming and hunting.
Evidence shows that Homo sapiens' brain developed to a certain level for some reason that enabled them to hunt skillfully and feed on large quantities of large mammals and large earthbound birds.
For example, the number of large mammals such as kangaroos in Australia has decreased considerably tens of thousands of years ago. In North America, elephant population dropped sharply. Also, the population of large birds that cannot fly rapidly declined about a thousand years ago in Madagascar and New Zealand. Such sharp declines in population coincide with massive invasion of human population to those places. These large mammals decline in number sharply as they are eaten by human beings arrive at those places in large numbers. Humanity spread on the planet by repeating this process and has reached the population of 6 billion as a result.
I mentioned earlier that 99 percent of species that have existed up to now have become extinct. So from a biological viewpoint, it is not rare for species to become extinct. It occurs very commonly. However, extinction occurs less frequently the higher up you go in taxonomic division − such as "phylum", which is the group above "species" and divisions above that. The world of animals is roughly divided into 30 groups that are called "phylum", We are part of a phylum called "chordate", As you may know, sea squirt belongs to the same chordate phylum.
If you study the Earth's history, you will note that major extinction has taken place five times. The majority of life actually exists in the sea. When you look at life using large group life "genus", most life exist in the sea. Sea is also regarded as the place where life originated. It is also the place where life evolved and diversified.
As I mentioned earlier, things change very frequently on the "species" level, so I would like to talk about this matter from the level of "family". We are classified as Homo sapiens of the Hominidae family, Homo genus. And we will look into it from this level. If you look at the changes by million years, it increases gradually until you reach a certain point where it experiences a big drop. The severest drop occurred at the last phase of Permian Period when about half of the marine organism families disappeared. Turning points in geological periods are symbolised by some drastic change and results in significant changes in organisms. The major extinction of the Permian Period eliminated half of marine organism families. It is said that 96 percent of marine life became extinct at the time on the "species" level. That was the severity of the change that occurred at that point. It recovered after that and fell sharply again at the end of the Cretaceous period. Today, the number of families in the sea has been increasing. Generally speaking, diversity of organisms has been increasing over time but suddenly drops once in a while. There are various theories about the cause of this sudden drop − such as collision of a meteorite − but we don't know what really happened. At any rate, it suddenly drops here. Many organisms disappeared at the end of the Permian Period and created an ecological vacancy all over the place. Reptiles that survived proliferated and diversified rapidly and created the age of dinosaurs. However, the dinosaurs eventually went extinct and our ancestors − the mammals that lives maintained low profile − flourished rapidly and created the Earth we have today.
Let us now take a look at how much we are consuming. Plants are said to be producing approximately 1011 tons of carbohydrates in one year. Actually, human beings are said to be consuming about 5 percent of this. Consumption in this case includes indirect consumption of animal feed. We also use plants for clothing and to build houses. So the amount we consume in total is estimated to be close to that produced by plants. I don't know if this estimation is truly correct, but that's what is said in the books anyway. To put it another way, Homo sapiens are using a considerable portion of the plants that are being created each year. The same is also true with freshwater. Water is also found in rocks under the ground, but we are unable to use it. So if you just calculate the freshwater on earth surface, we are using about a third of freshwater.
We are exerting severe impact on the overall system of Earth in this manner, and, as a result, the present rate of extinction is said to be faster by three to four digits than the extinction that occurred during the Permian Period, the greatest extinction from a geological viewpoint that eliminated 96 percent of species and half of families in the sea.
The time scale of extinction I mentioned earlier was based on the unit of million years, so we are thinking in terms of millions and hundred millions of years. But in this case, a decline of 20 to 30 percent have has occurred over the last 2 to 3 hundred years. The major extinction of the Permian Period occurred over a period of millions of years. In contrast, today's extinction is occurring over a period of hundreds of years. Almost identical phenomena are taking place in time scales that are tens of thousand times apart. This is not a question of whether it is good or bad. This is what is happening in reality.
As I mentioned at the outset, even we biologists do not know the existence of 99 percent of life on this planet. Many species of life are rapidly disappearing. I also do not have the answer as to how we can solve this problem. I do not have the answer, but I think that there is no tomorrow unless we concentrate the wisdom of the people who have gathered here today − the politicians, the bureaucrats and experts in various fields as well as many guests from abroad − to avoid the problem.
We talk about a range of today's issues such as environment and food, but from my point of view, they all originate from the problem of population. Humanity has no future unless we solve the population problem.
There are at least 3 ways to go about solving this problem. One is to "kill each other" or "starve to death" or "become fatally ill", as we see happening now in some parts of the world. We may succeed in solving the population problem if did these all over the world. But we cannot afford to solve the problem through such horrible means.
An alternative to this would be to aim for a softer landing. Biologists of earlier generation suggested we call our species Homo sapiens, which means "wise man". I think we can solve this problem if we are really wise and "sapiens", but I do not know the concrete method for doing so.
Thank you for your attention.