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Definition: Baer, Karl Ernst von from The Columbia Encyclopedia

1792–1876, Estonian biologist. He was a professor at Würzburg and Königsberg and from 1834 at St. Petersburg. Considered a founder of modern embryology, he discovered the notochord as well as the mammalian ovum. In his History of the Development of Animals (2 vol., 1828–37) he presented the theory of embryonic germ layers (the development of body tissues and organs from definite layers of cells formed in the early embryonic stages) and showed that the development of the embryo in different animals is similar in its early stages. He made these ideas a basis for a general evolutionary theory.


Summary Article: Baer, Karl Ernst Ritter von (1792-1876)
from Encyclopedia of Time: Science, Philosophy, Theology, & Culture

Karl Ernst Ritter von Baer was the modern founder of embryology and comparative embryology, as well as an accomplished zoologist and biologist. No longer a familiar name, Baer was in his time a genius acknowledged by his greatest contemporaries in science.

Baer was born in Landgut-Piep, Estonia, on February 17, 1792, into a rather wealthy aristocratic German-speaking family. At that time, Estonia was part of Russia, and Baer was a patriotic Russian.

The young nobleman studied medicine at Tartu, Estonia, and then Würzburg, Berlin, and Vienna, from 1810 to 1814. Only 3 years later he became director of the zoological museum at Königsberg, Germany. Baer's scientific genius went beyond anything wealth and privilege alone could supply, however.

He wrote a treatise in Latin on mammalian eggs and human origins in 1827; in fact, Baer had discovered a mammalian egg in the Graafian follicle, settling specific questions about human procreation. Baer also discovered the notochord in early vertebrate embryos.

The rest of his published works were in German. A preeminent man of science in Germany, Alexander von Humboldt, presented Baer with a medal from the French Academy. Much later, Albert Einstein wrote a short piece on Baer's law. Baer's law states that erosion is greater on the right bank of rivers in the northern hemisphere and greater on the left bank in the southern hemisphere, a law that perhaps occurred to him as he studied the fishes of the Caspian and Baltic seas.

Yet Karl Ernst von Baer “led two entirely different scientific lives, the first in Prussia, the second in Czarist Russia,” as Jane Oppenheimer described his career.

In 1834 Baer became Professor of Zoology and Anatomy at St. Petersburg in the Russian Empire.

Not an evolutionist, he criticized the ideas of Charles Darwin. Baer favored instead his own notion of “developmental history” (Entwicklungsgeschichte). Baer discovered that the stages of embryonic development of higher animals resemble the stages of embryonic development of lower animals. Embryos of one species may be indistinguishable from the embryo of a much higher creature. This notion of developmental stages proved important for the rise of evolutionary theory.

He worked on his major project on the developmental history of the animal kingdom, üeber Entwicklungsgeschichte der Tiere, from 1828 to 1837. Like Aristotle long before him, Baer studied chick embryos. And like Aristotle, Baer endorsed the notion of epigenesis (that the embryo becomes progressively more complex).

He also studied fishes and wrote in particular of his investigations into their developmental histories in a separate work in 1835. Baer showed that vertebrate organs derived from germ layers by differentiation, an important scientific discovery. He also demonstrated that embryos of higher animals share analogous features in embryonic development, the so-called biogenetic law. Embryos of higher animals develop through stages analogous to those of lower animals; that is, features specific to the specimen appear only after more general features have developed. Or, in the developmental history of the organism, general traits develop first.

Baer's fame spread beyond Prussia and the Russian Empire. He became a member of the French Academy of Scientists in 1858 and received the Copley medal from the Royal Society 9 years later.

Charles Darwin, in “An Historical Sketch of the Progress of Opinion on the Origin of the Species,” wrote, “Von Baer, towards whom all zoologists feel so profound a respect, expressed about the year 1858 … his conviction, chiefly grounded on the laws of geographical distribution, that forms now perfectly distinct have descended from a single parent-form.” In Descent of Man, Darwin referred to him as “the illustrious Von Baer” and commended Baer's observation that “the wings and feet of birds, no less than the hands and feet of man, all arise from the same fundamental form.” Darwin gave his critic high praise, indeed: “Von Baer has defined advancement or progress in the organic scale better than anyone else, as resting on the amount of differentiation and specialization of the several parts of a being—when arrived at maturity, as I should be inclined to add” (Festrede, 1862).

Obviously, Baer's ideas contributed to evolutionary thought without his having accepted Darwin's theory.

Vladimir Vernadsky credited von Baer with developing the ideas of carbon and nitrogen cycles.

Late in life, Baer wrote his autobiography and published a series of speeches and short essays on widely varied subjects. He was a respected man of science until the end. Karl Ernst Ritter von Baer died November 16, 1876, in Dorpat, Estonia.

Baer on Time

Baer published a speech connecting the perception of time with the rate of pulse in mammals. His scientific paper “Welche Auffassung der lebenden Natur ist die richtige? Und wie ist diese Auffassung auf die Entomologie anzuwenden?” was delivered as the commemorative address to the opening of the Russian Entomological Society in October 1860. It raised the following questions: Which conception of living nature is the correct one? And how is this conception to be applied in entomology? To answer the first question, Baer found it necessary to discuss the ultimate grounds of nature: time and space.

Absolute Nonpersistence in Nature

Concerning time, the constant alteration found in nature is nothing less than a continual development, a continual evolution. Persistence of substance does not occur over time. What humans take to be persistent existence is due entirely to the human scale of time, which is far too short. If we compare this scale of time to the grand relations in nature, we discover that humans cannot take themselves to be the measure for space and time. For measurement of space, humans have taken their various body parts as standard units. Although such units may well suffice for the immediate environs, or even for the earth's surface, they shrink and disappear in contrast to the spaces of the universe and even then only to those expanses visible to the human eye. When astronomers contemplate vast astronomical distances, they use units of measurement that are more comprehensible; the distance from the earth to the sun, for example. Yet this distance is some 92 million miles, a distance very hard to grasp. Baer noted that light travels so fast that it covers this distance in only 8 minutes. If we expand our scale to the distance light travels in a year, then the distances involved in measuring the cosmos go beyond human intuition and can be expressed only in scientific notation.

To measure time, humans have adopted regularly recurring physical natural phenomena to mark units of time, whether it be the day, month, or year.

Baer considered it indubitable that the standard brief unit of time, the second, was taken from the human pulse rate, as it remains fairly steady within the individual from second to second. This is a measure of time derived from our own biological processes, but we can do no other, observed Baer. Far shorter would be the time required to become aware of a sensory impression. Such measurement of time according to a sensation has been used by all peoples, said Baer. The German word Augenblick, which means “moment,” is literally the “blink of an eye.” Such examples can be adduced at length. And yet, because lively impressions are registered quickly and dull ones slowly, there can be no generally valid measure of the duration of a sensory impression, though Baer estimated it to be between 1/6 and 1/10 of a second. The speed of the faculty of perception is, for Baer, the true and natural unit of measurement for life. “In general, it appears that the pulse stands in a definite relationship with the rapidity of sensation and movement. The pulse of rabbits is twice as fast as that of man, and children only half as fast [as adult human beings]” (p. 258). But as rabbits perceive more quickly than do children, rabbits apparently experience much more in the same amount of time. Thus the speed of the faculty of perception sets the standard of “objective” time for a species.

In his address to the Russian Entomological Society, Baer wanted to make clear that “the inner life of a human being or animal can pass more quickly or more slowly, in the same amount of objective time, and that this inner life is the standard with which we measure time in the observation of nature” (p. 258). It is only because this fundamental standard is so small that we presume an animal that we observe in nature maintains a unified size and structure. In fact the animal has changed, if ever so slightly, due to breathing and blood circulation. It has undergone countless minute changes at the cellular level in its intestines, and so on. If we observed it not for an instant, but for a day or longer, we would notice some changes in the animal.

Baer's First Thought Experiment Concerning Time

To his audience in St. Petersburg, Baer posed a fascinating thought experiment. “If we imagine for a moment that the pace of life in man were to pass much faster or much slower, then we would soon discover that, for him, all the relations of nature would appear entirely differently” (p. 259). If we can take 80 years as an advanced age, then the life duration of such a man would be 29,200 days and as many nights. Now imagine that such a long life were condensed a thousandfold. After 29 days, he would already have reached invalidity. To ensure that none of his inner experience is lost, however, his pulse rate would have to be multiplied a thousandfold, so that he would still experience 6 to 10 sensory impressions per pulse beat. Baer observed first that such a man—Baer called him the “man of a month” (Monaten-Mensch)—would see many things that a normal man would not. He would see cannon balls streak by, which we would not be able to see because they change position too fast for us to perceive. A man of months would see the moon go through its cycle only once and so might well infer that it began as a crescent, grew larger and fuller, until it disappeared altogether. Such a man would, though, have no conception of seasons and would be flabbergasted to know that his environs would be covered with snow, that water would freeze in winter, for example. Similarly, due to our small time horizons, we find it difficult to imagine Earth during the Ice Age or to realize that the poles were once covered with rain forest or that our nation was once covered deep in a glacier for millennia.

Baer noted, secondly, the supposition of 29 days as a life span, and the compression of years a thousandfold, to be rather arbitrary. Indeed, the compression could have been much greater, as many life forms complete their life cycle in less than 29 days. Mushrooms, protozoa, and many insects complete their life cycles in but a few days.

Suppose, then, that we shorten human life. Instead of living 80 years, let us take a man who lives but 40 years, with an additional compression of a thousandfold; then man would live only 21 minutes. Nature would look very different to such a man, whom Baer called the “man of minutes” (Minuten-Mensch). He would form no concept of day and night (at least by direct experience) and would see the sun sink only slightly over his entire existence, and the stars and moon would not appear to change at all. Further, what would such a man know of changes in vegetation and the organic world generally? If he spent half his life watching a bud bloom in 20 minutes, he would still not know the full developmental course of the bud. Thus, for the man of minutes, flowers, grass, and trees would seem to be unalterable entities. Even the movements of animals would not be seen by him, because their limbs would be moving far too slow for his rapid eyesight to be seen. If he lived under the night sky, the man of minutes would conclude that the stars rise from the horizon for a short period. He would be justified in concluding—because he would not be able to see the full course of the stars repeatedly or even once—that the stars only go so far above the horizon and then set again, or that they cease motion or behave in ways that stars do not in fact behave. Or he might conclude that the stars do not move, but only Earth's horizon. He would never be able to verify which possibility is true after only 20 minutes of observation. The entire organic world would appear lifeless to the man of minutes. If he lived under the day sky, he would have no reason to believe that the sun sets completely and night occurs, or that the sun would ever appear again on a new day. All the sounds that we hear would be inaudible for the man of minutes; he, in turn, might hear sounds that we could not, assuming that his ears are configured the same as ours. Our ears hear sounds only between 14 and 48,000 vibrations per second. Faster or slower vibrations we cannot perceive at all. Indeed, Baer hypothesized, the man of minutes would only hear, and not see, light.

As if this astounding thought experiment were not enough, Baer posed a further experiment to his audience. Let us take a man, whose senses remain structurally human. Let us speed up his perceptions not only a thousandfold, but instead a millionfold. But let all the rest of nature remain as it exists. Baer inferred that such a man of milliseconds would perceive the vibrations of “aether,” which he hypothesized was several hundred billion vibrations per second, and which he hypothesized we see as color and light, would actually become audible, given that his sensory apparatus had such capacities. Aside from the later rejection of aether as a scientific hypothesis, Baer's point seems rational: Anything vibrating in the range of hundreds of billions per second would become audible to the man of milliseconds. Likewise, perhaps some ranges of vibration are perceived by human beings as sound, which the man of milliseconds would perceive as color and light. Based on recent experiments, Baer suggested that radiant heat consists of vibrations. Though he lived before the discovery of X-rays and radio waves, Baer went on to suggest that there might be many phenomena around us that we perceive as nothing at all. He considered the notion not at all counterintuitive, and modern science is replete with examples that validate his idea. Baer's ideas reached a sort of blend of science and poetry when he suggested that the planets might make a harmony of the spheres “for ears other than our own.” But in case his audience thought him flip about his line of inference, Baer said he very sincerely wanted to “prove that, had our innate sense of time been otherwise, nature would present itself to us differently, not merely shorter or longer in her processes and narrower or wider in her effects, but rather as something entirely different” (p. 264).

Baer's Second Thought Experiment Concerning Time

Having completed his first thought experiment, Baer posed a second thought experiment to what must have been an audience in rapt attention.

We have, previous to this point, shortened the human life in relation to the external world…. Let us now, conversely, lengthen it. Imagine, then, that our pulse were to go l/1000th as slow as it actually goes. And we allow the time required for sensation to be a thousandfold increased over what we require now. If we assumed the same amount of experience, then the life time of such a person would reach a “ripe old age” at approximately 80,000 years. With such an altered standard, which we take from our own life processes, the entire picture would look otherwise. A year would seem like 8.75 hours. We would lose our ability to watch ice melt, to feel earthquakes, to watch trees sprout leaves, slowly bear fruit and then shed leaves. (Festrede)

Such a man would truly be able to see change in the enormity of a mountain range being born. We would no longer notice the lifetimes of mushrooms or lesser animals such as insects. We would be able to see flowers only once already bloomed, and then only to disappear. Only the great trees would attain our notice and gain some meaning for us in their slower aging, Baer conjectured. The sun would probably appear to leave a tail in its wake, similar to the tail of a comet or the tracer from a cannonball.

As if this thought experiment were not enough, Baer finally asked his audience to imagine this 80-millennial human lifespan multiplied a thousandfold. That is, imagine a man living 80 million years in Earth time, but who would have only 189 perceptions in an entire Earth year. So every perception would require almost 48 hours to complete. Only 31.5 pulse beats would occur in the body in an entire Earth year. “If we increase the magnitude of the man's life, which has already been slowed a thousandfold, by another thousandfold, he would experience external nature completely differently again.” Such an 80-million-year man would not perceive the sun as a discreet circle but would see it as a glowing solar ecliptic, somewhat less bright in winter. The change of seasons would be a whirlwind: For only 10 pulse beats of the year, Earth would be snow and ice; for 1.5 pulses the melting snow would drench the land in spring; and for another 10 pulses, Earth would turn green.

Conclusions From the Experiments

With this observation Baer ended his second thought experiment concerning time. He was at pains to point out to his audience that these experiments in thought had not presupposed any new senses for man in order to experience different relations of time in nature. He observed that other animals have perceptions not accessible to man. So an alteration in man's senses would give humankind an entirely different picture of the world.

We have taken man quite simply as he is [said Baer] and only asked how the entirety of nature would appear to him, if he carried inside himself a different standard of time.—It is indubitable that man can measure nature, both space and time, only according to himself, because an absolute standard does not exist. Earth's surface seems very large to him, because he can see across only a very small portion of it. But the same is only very small in relation to the Sun or to the universe. If man had the size of only a microscopic monad, even if he were to retain the entire sharpness of his intellect, a pond would appear as immense as an ocean.—It cannot be otherwise with his standard of time, by which we measure the effectiveness of nature, because we can measure only extension by standards of space. In fact, we have seen that the narrower we take man's innate measure of time to be, the more rigid and lifeless the entirety of nature appears to be, until finally, due to the brevity of life, the passage from day to night would not be observable whatsoever, (p. 267)

Baer's thought experiments concerning time have proven his grand metaphysical claim at the beginning of his address to the Russian Entomological Society. Because the physical forces that are inherent in water, heat, and light wear away everything in nature, the audience may no longer doubt that all apparent persistence is only transitory.

With a resonance of the metaphysics of Heraclitus, Baer grandly concluded that “ all persistence is only an appearance. Becoming, in the form of development, is the true and persisting thing, through which all individual things are created in passing” (pp. 268-269). Baer's ideas went well beyond entomology into physics and beyond physics to infer what is ultimately real. “Matter in itself (Stoff an sick) and force in itself (Kraft an sick) exist only in the mental faculties. They are mere abstractions of our understanding. In reality no matter exists without properties (powers), just as we know no force which does not work from matter. Both are transitory, however, and the laws of nature are the remaining necessities by which they alter each other” (p. 269).

Thus we find in Baer's vision a world of relational forces and a set of natural laws by which the forces work. The organism measures time according to endogenous processes, primarily pulse rate, and for each organism, time begins and ends with the stages of its own developmental history.

See also

Darwin, Charles, DNA, Evolution, Organic, Experiments, Thought, Gestation Period, Haeckel, Ernst, Time, Perspectives of, Time, Relativity of


  • Appleman, P. (Ed.). ( (1979).). The descent of man: Darwin (2nd ed.). New York: Norton.
  • Baer, K. E.von, R.. ( (1862).). Festrede zur Eröffnung der russischen entomologischen Gesellschaft im Mai 1860. Berlin.
  • Oppenheimer, J. P (1990). Science and nationality: The case of Karl Ernst von Baer (1792-1876). Proceedings of the American Philosophical Society , 134(2), 75-82.
  • Whitlock, Greg
    Copyright © 2009 by SAGE Publications, Inc.

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