10 homínidos extintos

Desde al menos la época de los antiguos filósofos griegos, hemos estado comparando a la raza humana con los otros animales que habitan este mundo. Nos impulsan los mismos instintos e impulsos que los animales, pero los humanos somos infinitamente más complejos en emociones y pensamientos. Varios avances en los últimos dos siglos nos han ayudado a explicar esto. Y, sin embargo, quedan muchas preguntas.

En el siglo XVIII, Carolus Linnaeus diseñó un sistema de nombres basado en el latín para las especies del planeta y etiquetó a la nuestra como Homo sapiens , que significa "hombre sabio". En 1859, Charles Darwin publicó sus teorías sobre la selección natural , o cómo las especies cambian al adaptarse a su entorno: es más probable que los individuos con rasgos exitosos sobrevivan para transmitir esos rasgos. Después de muchas generaciones, por lo tanto, toda la especie rechaza algunos rasgos y adopta otros.

Tal evolución de chimpancé a humano llevaría muchos milenios. Afortunadamente, los arqueólogos han descubierto muchos tipos diferentes de fósiles de especies extintas que muestran similitudes tanto con los chimpancés como con los humanos. Al examinar la estructura ósea, los dientes y el ADN, los investigadores pueden hacer conjeturas informadas sobre la movilidad, la dieta, el tamaño del cerebro, la edad de estas especies y cómo podríamos estar relacionados.

Los homínidos son el grupo de especies que incluye humanos, chimpancés, gorilas y orangutanes además de sus ancestros inmediatos. ( Los homínidos son una subfamilia de homínidos que incluye el género Homo y sus ancestros o parientes inmediatos). La historia de los homínidos no es una línea recta desde los chimpancés hasta los humanos, sino un árbol genealógico diverso que aún se debate y ensambla a medida que encontramos más fósiles. Exploraremos las especies que nos precedieron, muchas de las cuales prosperaron durante mucho más tiempo que el Homo sapiens .

1. Ardipithecus Ramidus
2. Australopithecus afarensis
3. Australopithecus africano
4. Paranthropus Boisei
5. Homo habilis
6. Homo georgicus
7. homo ergaster
8. Homo erectus
9. Homo heidelbergensis
10. Homo neanderthalensis

Es un momento emocionante para la arqueología porque todavía estamos descubriendo fascinantes artefactos y fósiles que nos dan pistas sobre la historia de los homínidos. Recientemente, en 2009, los arqueólogos encontraron "Ardi", un esqueleto sorprendentemente intacto de la especie Ardipithecus ramidus , una de las primeras especies conocidas de homínidos extintos. Ardi y su familia existieron hace unos 4,5 millones de años en lo que ahora es Etiopía [fuente: Roberts ].

Los paleoantropólogos están interesados ​​en estudiar cómo se movían nuestros antepasados ​​homínidos. Específicamente, les gustaría señalar cuándo y cómo se desarrolló el bipedalismo, que es un avance significativo que nos distingue de nuestros antepasados ​​primates porque es más eficiente energéticamente que caminar sobre cuatro patas.

Finding so much of Ardi's skeleton, rather than just the skull and teeth of the species we had found before, was a major discovery. It revealed much of Ardi's body structure. Ardi's arms and fingers were long with short palms and wrists that were likely flexible. The pelvis was short and broad, and the feet could both grasp and support bipedalism. All of this suggests that Ardi climbed trees, could probably walk on two feet and didn't use her knuckles for walking much [source: Roberts].

Other environmental evidence suggests Ardi lived among trees and shrubs, which called into question the prevailing theory at the time that bipedalism developed on the savanna [source: Smithsonian].

Afortunadamente, sabemos bastante sobre Australopithecus afarensis . Desde la década de 1970, los arqueólogos han descubierto muchos especímenes de la especie en Kenia, Tanzania y Etiopía. Tenemos gran parte del esqueleto de un adulto y la mayor parte del esqueleto de un bebé, además de fragmentos de extremidades, mandíbulas y cráneos.

Un espécimen , apodado "Lucy", medía alrededor de 3,5 pies de alto (alrededor de 1 metro), y otro espécimen, llamado "Kadanuumuu", que significa "hombre grande", medía de 5 a 5,5 pies de alto (1,5 a 1,7 metros). Como podemos ver, esta especie tenía un importante dimorfismo sexual , lo que significa que los machos y las hembras de la especie tenían diferentes tamaños, a diferencia de Ardipithecus ramidus , por ejemplo. Los paleoantropólogos especulan que los machos y las hembras de la especie ramidus tenían más probabilidades de compartir tareas como la recolección de alimentos y el cuidado de los niños, mientras que los machos afarensis tenían más probabilidades de haber competido por el dominio. Algunos argumentan, sin embargo, que los especímenes más pequeños y más grandes de afarensisno representan machos y hembras de la misma especie, sino especies completamente diferentes [fuente: Roberts ].

A partir de la datación de capas de ceniza volcánica, los expertos estiman que el afarensis vivió hace entre 3,7 y 3 millones de años. Según los dientes de afarensis , los expertos suponen que comía principalmente plantas, incluidas frutas, hojas y semillas, pero también posiblemente lagartos [fuente: Smithsonian ].

Los cráneos de la especie revelan una caja craneana pequeña pero una cara y mandíbulas grandes. Con brazos largos y dedos curvos, la especie probablemente trepaba a los árboles. Pero el tórax, las formas de las piernas y la articulación de la rodilla sugieren que la especie caminaba erguida. Todo esto indica que afarensis podría ser un ancestro directo del género Homo , y por tanto de todos los humanos.

La especie Australopithecus africanus ocupa un lugar especial en la historia de la arqueología y la paleoantropología porque su descubrimiento e identificación como uno de los primeros homínidos en la década de 1920 nos ayudó a identificar África como el hogar de los antepasados ​​humanos.

Viviendo hace entre 3,3 millones y 2,1 millones de años en Sudáfrica, africanus tenía un cerebro más grande y dientes más pequeños que la especie más antigua afarensis . Su rostro también es más corto y se parece más a un rostro humano. La evidencia de los brazos largos, los hombros móviles y las manos grandes indican que la especie podía trepar, pero los huesos de las piernas, la pelvis y los pies sugieren que esta especie también era bípeda [fuente: Roberts ].

Paleoanthropologists once thought this species to be a hunter and even called it the "killer ape" because of evidence of broken animal bones near the hominid fossils. However, experts now believe that, rather than being the hunter, africanus was likely the hunted. Other predators probably preyed on these animals found near africanus, and dental evidence suggests africanus mostly ate plants and probably insects and eggs [source: Smithsonian].

Living between 2.3 million and 1.4 million years ago across Tanzania, Ethiopia and Kenya, Paranthropus boisei thrived for about 1 million years. Unfortunately we have yet to uncover any specimens for the body or limbs, but we do have a few specimens of the skull, jaw and teeth that indicate how fascinating this species was.

Boisei is nicknamed "nutcracker man" because of its large teeth and strong jaws. However, wear on the teeth suggests that although they could chew hard foods, they commonly didn't. The skull is short from front to back but has wide cheekbones and wide eye sockets. The fact that boisei's face didn't project as much as earlier hominid species suggests a progression toward more humanlike characteristics.

Another significant aspect of this find was that it marked the first use of a method called potassium/argon (K/Ar) dating for determining the age of volcanic ash . This was helpful because volcanic ash covered the surface, forming a lasting layer. When we discover fossils in between layers, we can reliably narrow down the age of those fossils. And, in some cases, volcanic ash even captured and preserved footprints of ancient hominids. After this development, paleoanthropologists found that the process of human evolution is far older and longer than previously believed.

In addition, the discovery that boisei lived at the same time as Homo erectus helped paleoanthropologists determine that the history and lineage of hominids was not a straight line but a tree with various branches [source: Smithsonian].

Fossils of Homo habilis show evidence of long arms and a projecting face more similar to apes, but the species also had more humanlike traits than older species, including a larger brain and a smaller face and teeth [source: Smithsonian]. Perhaps members of this species adapted smaller teeth as they learned to eat more energy-efficient foods that required less chewing [source: Roberts].

Paleoanthropologists speculate that this species could be associated with the earliest known evidence of bones that had been cut and hammered. This would mean they ate meat and bone marrow, and dental evidence does not contradict this idea.

Although Homo habilis's name means "handy man," it may not have been the first hominid to make stone tools, as was once thought. We've found stone tools that date back to a period when several hominids existed, and they date earlier than the oldest known member of the genus Homo [source: Smithsonian].

Homo habilis lived 2.4 million to 1.4 million years ago across Kenya, Ethiopia and South Africa, and you'll notice that this is the earliest example of the genus Homo. However, classifying it as thus required tweaking the definition of the genus by lowering the brain size requirement. In 2000, archaeologists discovered both a comparatively young habilis fossil at only 1.44 million years old and a slightly older Homo erectus at 1.55 million years old. Discovering these in the same region of northern Kenya suggests that these species didn't evolve one after the other, but rather co-existed [source: Smithsonian].

Because many of the fossils we unearth are incomplete and tell only a partial story, categorizing them into distinct species becomes fuzzy and controversial. Such is the case with Homo georgicus, which may not be its own species, but rather a member of Homo erectus. Regardless, the trove of this hominid's fossils found in Dmanisi, Georgia, is fascinating.

Archaeologists unearthed several skulls and jaws in addition to fragments of limbs, hands and feet. These fossils date to 1.8 million years ago and represent the earliest known hominid to have lived outside of Africa . Although proportionally georgicus was similar to modern humans in body structure, this species had a relatively small brain and stood shorter at just under 5 feet tall (1.5 meters).

Amazingly, one of the skulls shows evidence that the individual survived for a while after having lost all of his or her teeth. In a more primitive culture, this would have been impossible. But this is evidence that a supportive societal structure existed and helped take care of this individual [source: Roberts].

In 1984, archaeologists discovered a striking example of Homo ergaster in the skeleton known as "Turkana Boy" (after having been found in Turkana, Kenya). Before, all we had to tell us about ergaster was a lower jaw, but Turkana Boy is a nearly complete skeleton, revealing much more. He had a narrow pelvis that indicates he was very comfortable walking upright on two feet. His arms were shorter and his legs were longer than his predecessors.

What's perhaps most striking is how tall Turkana Boy was. Although he was likely not fully grown, he grew to 5.25 feet tall (1.6 meters) before he died, meaning ergaster is the first of the genus Homo we know of that reached the height of modern humans [source: Roberts]. It is difficult to estimate the age of death for many hominid fossils because they also had different growth patterns and a shorter adolescence than modern humans, but judging from the teeth, experts believe Turkana boy was probably 8 or 9 years old [source: Smithsonian].

Other fossils have been found in Tanzania, Ethiopia and South Africa. Homo ergaster lived 1.9 million to 1.5 million years ago, and its name means "workman," stemming from the fact that the species made tools from stone, such as the Archeulean handaxe. This was a hand-held stone tool that was forged from striking flakes off to form a sharp edge, possibly used for butchery or chopping wood.

Evidence of Homo erectus or "upright man" was originally discovered in 1891 on the island of Java in Indonesia. This species lived as far back as 1.8 million years ago to as recently as 30,000 years ago. Skull fossils show that this species had a long cranial vault housing a relatively large brain, in addition to a wide face and strong brow.

Most of what we have of erectus consists of skulls, jaws and teeth, but we also have one complete thighbone. These have been discovered across Asia, and some similar-looking fossils have been found in Africa, but researchers debate whether these belong to the same species.

Considering the limited fossil record for this species, Paleoanthropologists have still been able to surmise that erectus was tall and walked upright. The handaxes found in Africa are notably absent in Asia, however, suggesting that the species likely left Africa before their invention or that they made tools from other available materials [source: Roberts].

Having lived in Europe 600,000 to 200,000 years ago (during the Middle Pleistocene era), Homo heidelbergensis was likely the first hominid species to have lived in a cold climate. To thrive in such an environment necessitated several momentous innovations. This included building shelters : In France, evidence of postholes dates back 400,000 years.

They also probably mastered fire: In Israel, evidence of burnt wood and tools forged in fire date to 790,000 years ago [source: Smithsonian]. Evidence of various sturdy tools and large butchered animal remains suggests that heidelbergensis was also an adept hunter.

Esta especie obtuvo su nombre porque se encontró por primera vez cerca de Heidelberg, Alemania, en 1907. Desde entonces, los arqueólogos han descubierto un esqueleto casi completo que incluye un cráneo que albergaba un gran cerebro dentro del rango del tamaño humano moderno. La pelvis es ligeramente ancha, lo que provocó el apodo de "Elvis". De hecho, heidelbergensis comparte muchas similitudes con los humanos modernos, y las excepciones suelen estar más cerca de los fósiles de los neandertales, lo que sugiere que esta especie podría ser nuestro ancestro común [fuente: Roberts ].

Los neandertales , también conocidos como Homo neanderthalensis , son los parientes más cercanos conocidos a los humanos modernos, y hemos descubierto varios esqueletos completos de la especie. Por lo tanto, sabemos bastante sobre ellos, pero queda mucho por aclarar, incluido cómo encajan exactamente los neandertales en nuestro árbol genealógico. La evidencia muestra que los humanos modernos se cruzaron con los neandertales, pero que no evolucionamos a partir de ellos.

This species thrived across Europe and even into Asia. They tended to be shorter and wider than modern humans. They had wide shoulders, strong arms and legs and a large, deep chest. Paleoanthropologists speculate that the short stature could have been an adaptation to deal with the colder weather to conserve body heat. Another possible explanation is that this sturdier, tougher build was an adaptation to a brutal lifestyle. Indeed, the fossil remains show many injuries [source: Roberts]. They hunted animals and ate a lot of meat, but they also enjoyed seafood and plants. Plaque found on molars has revealed remains of starch grains [source: Smithsonian].

Los cerebros de los neandertales tendían a ser incluso más grandes que los nuestros, y la evidencia de su cultura sugiere un comportamiento muy diferente al de los primeros homínidos. Enterraban a sus muertos, vestían ropas primitivas y hasta elaboraban objetos ornamentales. Esto genera preguntas sobre la relación del tamaño del cerebro con el comportamiento social, la innovación y la imaginación .

Los paleoantropólogos están interesados ​​en la cuestión de cómo evolucionaron la inteligencia, el comportamiento y la cultura modernos. ¿Evolucionó junto con nuestra evolución física o sucedió más rápido? Es posible que nunca respondamos definitivamente a esta pregunta, pero con cada nuevo fósil desenterrado, nos acercamos más a la comprensión de nuestros antiguos antepasados.

Nota del autor: 10 homínidos extintos

Without having studied hominids before, several things struck me in my research. First, the age of these specimens is astounding. It's difficult to fathom how the world would look so long ago. That we have any fossils this old and we know so much about them is incredible. And yet, I don't want to make the mistake of thinking we know more than we do. Although we have sophisticated technology to inspect age, teeth, DNA, etc., many of our conclusions about their lives are only educated guesses. New fossils continually call into question previous notions. Clearly, we still have a lot to learn about the exact origins of humanity.

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