What Are The Closest Living Relatives To Animals

Bioinformatician Bernhard Haubold of the Max Planck Plant of Chemical Ecology provides this explanation:

Prototype: COURTESY OF BERNHARD HAUBOLD

Humans, chimpanzees, gorillas, orangutans and their extinct ancestors form a family of organisms known as the Hominidae. Researchers mostly agree that amid the living animals in this grouping, humans are most closely related to chimpanzees, judging from comparisons of anatomy and genetics.

If life is the result of "descent with modification," every bit Charles Darwin put it, we can try to represent its history as a kind of family tree derived from these morphological and genetic characteristics. The tips of such a tree testify organisms that are alive today. The nodes of the tree announce the common ancestors of all the tips connected to that node. Biologists refer to such nodes as the final common ancestor of a grouping of organisms, and all tips that connect to a particular node form a clade. In the diagram of the Hominidae at right, the clade designated by node 2 includes gorillas, humans and chimps. Within that clade the beast with which humans share the most recent common antecedent is the chimpanzee.

Source: COURTESY OF BERNHARD HAUBOLD

FAMILY TREE of the Hominidae shows that chimpanzees are our closest living relatives.

There are 2 major classes of show that allow u.s.a. to estimate how old a particular clade is: fossil data and comparative data from living organisms. Fossils are conceptually easy to interpret. Once the historic period of the fossil is determined (using radiocarbon or thermoluminescence dating techniques, for example), we then know that an ancestor of the organism in question existed at least that long ago. There are, however, few good fossils bachelor compared with the vast biodiversity around us. Thus, researchers likewise consider comparative information. Nosotros all know that siblings are more similar to each other than are cousins, which reflects the fact that siblings have a more than contempo mutual ancestor (parents) than do cousins (grandparents). Analogously, the greater similarity between humans and chimps than betwixt humans and plants is taken every bit prove that the last common ancestor of humans and chimps is far more than recent than the last common ancestor of humans and plants. Similarity, in this context, refers to morphological features such as eyes and skeletal structure.

1 problem with morphological data is that it is sometimes difficult to interpret. For instance, ascertaining which similarities resulted from common ancestry and which resulted from convergent evolution tin, on occasion, testify tricky. Furthermore, it is well-nigh impossible to obtain time estimates from these data. So despite analyses of anatomy, the evolutionary relationships among many groups of organisms remained unclear due to lack of suitable information.

This changed in the 1950s and 1960s when protein sequence information and Deoxyribonucleic acid sequence information, respectively, became available. The sequences of a poly peptide (say, hemoglobin) from ii organisms can be compared and the number of positions where the two sequences differ counted. It was presently learned from such studies that for a given protein, the number of amino acrid substitutions per year could--equally a start approximation--be treated equally abiding. This discovery became known every bit the "molecular clock." If the clock is calibrated using fossil data or data on continental drift, so the ages of various groups of organisms can theoretically exist calculated based on comparisons of their sequences.

Using such reasoning, information technology has been estimated that the last mutual ancestor of humans and chimpanzees (with whom nosotros share 99 percent of our genes) lived five million years ago. Going back a little farther, the Hominidae clade is thirteen million years old. If we continue farther back in time, nosotros find that placental mammals are betwixt 60 and 80 million years old and that the oldest 4-limbed animal, or tetrapod, lived between 300 and 350 1000000 years ago and the earliest chordates (animals with a notochord) appeared about 990 one thousand thousand years ago. Humans belong to each of these successively broader groups.

How far dorsum can we go in this way? If we try to trace all life on our planet, we are constrained by the world'south age of 4.5 billion years. The oldest bacteria-like fossils are 3.v billion years old, so this is the upper estimate for the age of life on the earth. The question is whether at some point before this date a final common ancestor for all forms of life, a "universal antecedent," existed. Over the past xxx years the underlying biochemical unity of all plants, animals and microbes has become increasingly apparent. All organisms share a like genetic machinery and sure biochemical motifs related to metabolism. It is therefore very likely that there in one case existed a universal ancestor and, in this sense, all things alive are related to each other. Information technology took more than than two billion years for this earliest form of life to evolve into the offset eukaryotic cell. This gave rise to the terminal common antecedent of plants, fungi and animals, which lived some 1.6 billion years ago.

The controversies surrounding biological evolution today reverberate the fact that biologists were tardily in accepting evolutionary thinking. I reason for this is that pregnant modifications of living things are difficult to observe during a lifetime. Darwin never saw development taking place in nature and had to rely on testify from fossils, as well as constitute and brute convenance. His idea that the differences observed within a species are transformed in time into differences between species remained the well-nigh plausible theory of biodiversity in his time, but there was an awkward lack of direct observations of this process. Today this situation has inverse. There are now a number of very striking accounts of evolution in nature, including exceptional piece of work on the finches of the Galapagos Islands--the same animals that first inspired Darwin'south work.

Further READING:

The Beak of the Finch : A Story of Evolution in Our Time (Vintage Books, 1995)

Source: https://www.scientificamerican.com/article/how-closely-related-are-h/

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