Dikika, la niña australopiteca

<English version below>

Tras el niño de Taung, uno de los homininos infantiles más famosos es Dik-1-1, un esqueleto casi completo de Australopithecus afarensis de 3,3 millones de años (Ma). Fue encontrado entre 2000 y 2003 en el sitio de Dikika cerca de Hadar (Etiopía), por Tilahun Gebreselassie, del equipo de Zeresenay Alemseged, del Instituto Max Planck de Antropología Evolutiva de Leipzig. Bernard Wood llamó a este hallazgo A precious little bundle“, un precioso pequeño puñado de huesos. Se tardaron seis años hasta conseguir separar los huesos del sedimento cementado donde se encontraban. Lo apodaron Selam (que significa Paz en amárico) e incluso Lucy’s baby, aunque en los últimos tiempos se ha generalizado un mayor uso del alias Dikika’s Baby o Niña de Dikika.

Los huesos conservados de la Niña de Dikika representan prácticamente todas las partes del esqueleto, y nos proporcionan una información valiosísima sobre la ontogénesis de su especie. A continuación resumo el conocimiento que nos ha dejado este pequeño individuo:

  • A partir de su dentición se ha estimado una edad de entre 3 y 4 años en el momento de su muerte. Toda la dentición decidua estaba presente, y las coronas de los primeros molares no habían erupcionado pero estaban plenamente formadas.
  • Su cráneo tiene similitudes con otros Australopithecus infantiles, como el propio Taung-1 o el afarensis juvenil AL 333-105. Su capacidad craneal era 235 cc, y se estima que habría alcanzado 425 cc de adulto.
  • El cerebro de Au. afarensis muestra un desarrollo lento, aproximándose al de los humanos, pero la dentición tiene un desarrollo más rápido y próximo de los simios africanos. Se encontraría alrededor del fin del periodo de lactancia.
  • Conserva el hueso hioides, que es muy difícil de encontrar fosilizado. El hioides de Selam tiene una cavidad en su base que sirve como saco de aire, como en Pan, mientras que este hueso es plano en Homo. Es decir, emitiría sonidos más parecidos a los de un chimpancé que a los de un humano.
  • Era un ser bípedo, según expresan la posición del foramen magnum y los huesos de las piernas.
  • Sin embargo, la escápula y los huesos curvados de las manos y los pies indican que conservaba cierta vida arbórea, capacidad para trepar y de balanceo, tal como se ha observado en otros especímenes de su especie. El entorno donde vivió se componía de praderas herbáceas y bosques de galería.
  • La morfología y organización de su columna vertebral presenta una forma transitoria hacia la humana y menos afín con la de los simios africanos. Tiene 7 vértebras cervicales y 12 vértebras torácicas como los humanos (los simios africanos tienen 13).

La región de Dikika está rodeada por tres grandes áreas de conocida riqueza de fósiles homininos:

  • Hadar, tan solo 10 km al norte, lugar del hallazgo de Lucy y de La primera familia (un grupo fosilizado de 17 individuos de Au. afarensis).
  • Gona al oeste, donde apareció una colección útiles líticos de 2,5 Ma.
  • Middle Awash al sur, zona de múltiples hallazgos de homininos de diversos periodos, como Ardi (Ardipithecus ramidus, 4,4 Ma), Bodo (Homo rhodesiensis, 600 ka) o Herto (Homo sapiens, 160 ka).

Más información:

  • Alemseged, Zeresenay et al. “A juvenile early hominin skeleton from Dikika, Ethiopia”. Nature volume 443, pages 296–301 (21 September 2006 [link].
  • Madison, Paige, “The Discovery of The Dikika Baby Fossil as Evidence for Australopithecine Growth and Development”. Embryo Project Encyclopedia (2015-02-02). ISSN: 1940-5030 [link].
  • Ward, Carol V. “Thoracic vertebral count and thoracolumbar transition in Australopithecus afarensis”. PNAS, 2017 [link].
  • The Afar Triangle, by Paige Madison | Nutcracker Man [link]. 
Niña de Dikika

Niña de Dikika. Esqueleto y detalle de cráneo y columna vertebral. Crédito: Zeray Alemseged

Dikika, the Australopithecine girl 

Sigue leyendo

The ‘Lomekwian’ technology?

Lately we have read much about the shocking study of 150 stone tools in Lomekwi, Kenya, close to Lake Turkana, dated to 3.3 mya: the oldest-known tools. They include flakes, cores, hammers and anvils. In fact they were found in 2011 and we already started to hear about them several weeks ago, but last week the news was widely spread. This discovery has a curious background with several controversials, which may help understand its potential importance:

  • 1) Dikika, Lower Awash (Ethiopia). In 2000 the famous Lucy’s baby specimen was found there. She was a 3-year old Australopithecus afarensis dated to 3.3 Ma. Her oficial name is ‘Selam’ which means peace. New excavations on that site in 2010 reported cut, linear marks on animal bones dated to 3.4 Ma. BUT no actual tools were found, so there were various opinions against the human action by-purpose, instead the cut marks might have been the result of trampling by humans or other animals. So, the idea of 3.4 Ma tools was more or less set aside. NOW this idea is ‘strongly’ reconsidered.
  • 2) Lomekwi (Kenya). In 1998 an interesting hominid specimen was found quite close (1 km away) to the site of the -now- famous tools. This was Kenyanthropus platyops, in theory different from Au. afarensis because of the smaller first molars, the flat lower face (however it is very distorted, so this may not be the actual morphology), and the small ear openings (similar to chimps and Au. anamensis). BUT no more relevant teeth were found (e.g. canines) nor post-cranial skeleton parts. NOW this hominid has regained much prominence because he could have been the author of the tools (same age, same location as the tools). Some argues that the stone tools may be more associated to Au. afarensis – but actually there is a parallel point to determine: if K. platyops could be just another population of australopitecines, given the enormous variation we really know about these.
lomekwi-zoom

Lomekwi-3 site (I) and zoom to the excavation (R) – yes, what you see are some of the famous stones!

Focusing on the tools themselves, there is no doubt that they reflect a sophisticated understanding 3.3 million years ago of how rocks break, as well as some fine motor skills to break them effectively. Previously the oldest-known evidences of stone tools were from 2.6 mya (zebra bones with tool cuts in Gona, Ethiopia) and then different sets of tools 2.35 mya in Omo and Hadar (Ethiopia) and 2.3 mya in Lokalalei (Kenya). Finding a human technology 700,000 years older, in this ancient time range, is really amazing! What also shocks me is the proposal to define a new technology based on these findings. They researches call it ‘Lomekwian’ obviously referring to their location, in contrast to the Oldowan technology (Mode 1). The rationale is basically based on 3 points:

  1. They are larger and heavier than Olduwan.
  2. They are apparently made by hitting against a passive hammer (like chimps do today to crack nuts), rather than holding the core with the hand like in Oldowan technique.
  3. The flakes extracted show more errors or ‘accidents’ than in Oldowan technique.
flake

Flake LOM3 2012 J17 3 – my favorite (Photo: africanfossils.org)

In the next years we will be fortunate to live a ‘reboot’ of the paleoanthropology studies of 3 million years ago. Very quickly, we have read about the new oldest candidates for the first Homo, and now about new oldest candidates for the first technology. The old equation Homo=Technology is probably destroyed: clearly, stone tools could have been invented by multiple lineages of early hominins. We already suspect that some bone points and piercers found in South Africa (Swartkrans and Kromdraai) could have been made by robust australopithecines 2 million years ago. Chimps today use hammers and anvils to break palm nuts…

chimps

Tools used by chimps: stone anvil, hammerstone with palm nuts, ant-dipping tool and spear (Photo: humanorigins.si.edu)

… Thefore, the development of ‘technology’ is not a milestone purely linked to the appearance of Homo. Probably the learning and social skills made early hominids to explore their technical abilities and to experiment with the resources around, like stones – for millions of years! Many experiments failed, but some of them succeeded and took part in the evolution processes -for some more hundreds of thousands of years- and so hominids learnt to produce stone flakes, cores, hammers and anvils.

Were the ‘Lomekwian’ tools one of those experiments, which maybe succeeded locally? Did it become a consistent, spread technology? For the moment, I think that it seems OK to call it ‘Lomekwian’, al least for identifying precisely those key findings. By the way, this is another basic criteria to use the controversial name ‘Kenyanthropus platyops’ for the remains I described above – that is, at least for identifying precisely what this is and where this comes from.