Hadar, Ethiopia

Administrative Zone 1 (Afar Region), Ethiopia

The region's rocks consist mainly of mudstones, siltstones, fine-grained sandstones and volcanic tuffs. The region of Hadar has been divided into four geologic members — Basal (~3.8–3.42 Ma), Sidi Hakoma (~3.42–3.26 Ma), Denen Dora (~3.26–3.2 Ma), and Kada Hadar (<~3.2 Ma)—with three tuffs (Sidi Hakoma Tuff [SHT], Triple Tuff [TT] and Kada Hadar Tuff [KHT]) separating the four members.

The Sidi Hakoma member tends towards high rainfall and low seasonality. The overlying Denan Dora Member was a grassland habitat. Finally, the Kada Hadar Member was an even more open and arid habitat, as seen in the high abundance of antilopines, which frequent these types of terrains.[3]

The first paleo-geological explorations of the Hadar area were conducted by Maurice Taieb. He found Hadar in December 1970 by following the Ledi River, which originates in the highlands north of Bati to empty into the Awash River. Taieb recovered several fossils in the area and led a party back to Hadar in May 1972. In October 1973, 16 individuals with the International Afar Research Expedition (IARE) arrived at Hadar and camped there for two months during which the first hominin fossil was found. (Taieb claims in his 1985 book Sur la Terre des premiers Hommes to have discovered the Hadar fields in 1968, but Kalb argues that claim to be incorrect.)[4] The IARE party examined a series of sedimentary layers called the Hadar Formation, which was dated to the late Pliocene to early Pleistocene epochs (3.5 to 2.3 million years ago).[5]

The anthropologist Donald Johanson, a member of the 1973 expedition to Hadar, returned the next year and discovered the fossil hominin "Lucy" in the late fall of 1974.[6] He spotted a right proximal ulna in a gully, followed by an occipital bone, a femur, some ribs, a pelvis, and a lower jaw. Within two weeks, nearly 40% of the hominoid skeleton had been identified and cataloged.[7] Lucy is the most famous fossil to have been found at Hadar. Lucy is among the oldest hominin fossils ever discovered[6] and was later given the taxonomic classification Australopithecus afarensis. (The name 'Lucy' was inspired by the song "Lucy in the Sky with Diamonds" by The Beatles, which happened to be playing on the radio at base camp.)

In 1975, Donald Johanson made another discovery at a nearby site in Hadar: 216 specimens from approximately 17 individuals, most likely related and varying in age, called AL 333 (colloquially referred to as the "First Family").

About thirty years later in nearby Dikika, another Australopithecus afarensis fossil skeleton was found in a separate outcrop of the Hadar Formation across the Awash River from Hadar. The skeleton is of a three-year-old girl later named "Selam," which means peace in Amharic Ethiopian languages.

Specimens and inferences

Location of the Hadar Formation and the Afar Triangle (Afar Depression), Ethiopia

In 1973 and 1974 when the first anatomical discoveries were made, their size and shape pointed towards a variety of taxa, but further research has confirmed that only one hominin taxon is present here. The first find there was a fossil knee joint estimated to date from 3.4 million years ago. Since then, the Hadar research area has yielded 370 specimens of A. afarensis, one specimen of Homo, and 7571 additional vertebrate specimens.

The specimens recovered display a variety of different primitive cranial post features, which indicate A. afarensis is distinct from other species of Australopithecus: small cranial capacity, palate similar to African apes (parallel tooth rows, shallow, long from front to back, narrow from side to side), primitive occipital, basal cranium anatomy, high frequency of unicuspid third premolars, prognathic face, and primitive mandibular anatomy. Postcranially, the pelvis, knee, ankle, and foot indicate habitual, terrestrial bipedalism, but ape-like curved finger and foot bones are retained ancestral ape-like features.[3]

According to the geological members of Hadar, the Awash River (top) and Omo Valley (bottom) biomes might resemble the Hadar paleoenvironment.

Other specimens discovered from the Hadar Formation contain a vast diversity of bovid species found in Africa. The bovids found in the formation included the Aepycerotini (Aepyceros), Alcelaphini (Damalborea and Parmularius), Antilopini (Gazella), Bovini (Ugandax and Pelorovis[?]), Caprini (Budorcas), Cephalophini, Hippotragini (Oryx), Neotragini (Raphicerus[?] and Madoqua), Reduncini (Kobus), and Tragelaphini (Tragelaphus)[8].[9][10] Artiodactyls outside the bovid family were present within the formation as well, namely the giraffids (Giraffa and Sivatherium), Hippopotamidae (Hippopotamus), and suids (Kolpochoerus, Notochoerus, and Nyanzachoerus).[11] While a definitive list of carnivorans found within the Hadar Formation has yet to be compiled, confirmed genera that were found within the Hadar Formation include canids (Canis and Nyctereutes), felids (Dinofelis,[12] Leptailurus, Felis, Homotherium, and Panthera), hyaenids (Chasmaporthetes, Ikelohyaena, Crocuta, Hyaena, and cf. Pliocrocuta),[13] herpestids (Herpestes and cf. Helogale), mustelids (Mellivora, Enhydriodon,[14] and cf. Poecilogale), and the viverrid (cf. Civettictis). Mammals within the formation outside the artiodactyl and carnivoran families include a bat (indeterminate), the leporid (Lepus), the equid (Eurygnathohippus),[15] rhinoceroses (Ceratotherium and Diceros),[16] old world primates (Parapapio, Theropithecus, and Cercopithecoides), proboscideans (the deinothere Deinotherium and elephants Elephas, Loxodonta, and Mammuthus) [17][18][19] old world porcupines (Hystrix and Xenohystrix),[20] murid rodents (Gerbilliscus, Acomys, Golunda, Oenomys, Praomys, Saidomys, Millardia, and Mus),[21] the spalacid Tachyoryctes, a squirrel indet., and an aardvark species. Taxons within other classes are present within the Hadar Formation as well, such as birds (Plectropterus, Balearica, Anhinga, and Struthio) and reptiles (Crocodylus, Python, Varanus, and Bitis).[22][23][24][25][26][27] [28][29]

Bovidae

Bovids of the Hadar Formation
Taxa	Species	Presence	Material	Notes	Images
Aepyceros	A. datoadeni	Kada Hadar Member at Hadar.	Near-complete skull lacking parts of horn cores(AL 787-1 KH1).[9]	Extinct relative of modern impala.
Beatragus	B. sp.		Detached braincase with two horn cores.[9]	Extinct relative of modern hirola.
Budorcas	B. churcheri[30]	Sida Hakoma member.[9]	Complete skull with horns (AL 136-5 DD2)[9]	Extinct relative of takin.
Damalops	D. sidihakomai.[31]	Sidi Hakoma member.	AL 208–7, a skull with horn cores, right P4–M3, and left M2–3.	Extinct genus of Alcelaphinae.
Damalborea	D. elisabethae	Basal Member and Sidi Hakoma member.[9]	A skull with horn cores (AL 208-07 SH3).[9]	Extinct genus of Alcelaphine bovids.
	D. grayi	Denen Dora and Kada Hadar Member. [9]	Multiple postcranial fragments such as horn cores, maxilla, and mandibles.[9]
Gazella	G. harmonae	Kada Hadar Member at Hadar.[9]	Skull remains such as isolated teeth, maxilla, frontlet, and occipital (AL 444-16). [9]	Extinct relatives of modern gazelles
	G. cf. janenschi	Denen Dora Member.	Horn cores (AL 302-6 DD).[9]
	G. cf. praethomsoni	Denen Dora and Kada Hadar Member	Few Horn core specimens.[9]
Hippotragini	Praedamalis deturi	Kada Hadar, Sida Hakoma, and Denen Dora member at Hadar.	Multiple specimens based on horn cores and lower teeth.[9]	Ancestor of modern day oryx.
Kobus	K. hadarensis	Sidi Hakoma, Kada Hadar and Denen Dora Member.		Extinct relatives of antelopes.
	K. oricornus	Denen Dora and Kada Hadar Member.	Several specimens of braincase and horn core. [9]
Madoqua	M. sp
Raphicerus	R. sp	Kada Hadar and Sidi Hakoma.	Mandibles and horn cores.[9]
Parmularius	P. pachyceras	Sidi Hakoma and Kada Hadar Member.[9]	Braincases and horn cores.[9]	Large extinct alcelphines related to topis and hartebeests
Pelorovis	P. sp.
Tragelaphus	T. lockwoodi	Basal Member and Sidi Hakoma Member.	Braincase with complete horn cores (AL 142-3 SH2).[9]	Extinct relatives of spiral-horned antelopes.
	T. rastafari	Basal, Sidi Hakoma, Denen Dora, and Kada Hadar Member.	Several horn core specimens.
Ugandax	U. coryndonae	Denen Dora and Sidi Hakoma member at Hadar.	Complete partial skull and horns (AL 194-1 DD1)[9]	Ancestor of Cape buffalo

Suidae

Suidaes of the Hadar Formation
Taxa	Species	Presence	Material	Notes	Images
Kolpochoerus	K. afarensis	Kada Hadar Member, Sidi Hakoma Member, and Denen Dora Member.[11]	Postcranial skulls, teeth fragments, and mandibles.	Extinct relatives of the pig family.
Notochoerus	N. eulius	Kada Hadar, Lower and Upper Sidi Hakoma Member, and Denen Dora Member.[11]	Postcranial skull, teeth, and mandibles.	a large pig in the extinct subfamily called Tetraconodontinae.
Nyanzachoerus	N. kanamensis	Basal member and Sidi Hakoma Member.[28]	Complete cranium, mandibles, and dentition.	Extinct genus of pig family that belongs to Tetraconodontinae.
	N. pattersoni	Basal Member, Lower and Upper Sidi Hakoma Member, and Denen Dora Member.[11]	Complete skulls, mandibles, and dentition.[11]

Felidae

Felids of the Hadar Formation
Taxa	Species	Presence	Material	Notes	Images
Dinofelis	D. aronoki	Kada Hadar Member[12]	Postcranial member: distal radius (AL-363-20)[12]	A sabertooth cat.
	D. petteri	Sidi Hakoma Member and Denen Dora Member. [12]	Postcranial member: partial humerus (AL 168-30), proximal ulna (AL 262-9), and right astragalus (Al 173-11)[12]	A sabertooth cat.
Felis	F. sp.
Homotherium	H. hadarensis	Denen Dora Member[23]	Complete cranium skull, mandible fragments (DIK-96-1), teeth, and forelimb.[23]	A sabertooth cat.
Megantereon	M. sp.
Leptailurus	L. sp.
Panthera	P. sp.

Deinotheriidae

Deinotheriidae of the Hadar Formation
Taxa	Species	Presence	Material	Notes	Images
Deinotherium	D. bozasi	Denen Dora Member, Kada Hadar Member and Sidi Hakoma Member.	Complete cranium skull and teeth fragments.	A large extinct elephant-like proboscidean.

Elephantidae

Elephantids of the Hadar Formation
Taxa	Species	Presence	Material	Notes	Images
Elephas	E. ekorensis	Sidi Hakoma and Denen Dora members of the Hadar Formation at Hadar and Dikika. [18]	Mandibles and molar fragments.	Extinct lineage related with Asian elephant.
Loxodonta	L. adaurora	Denen Dora Member and Sidi Hakoma Member at Hadar.[17]	Mandibles and molar fragments.	An extinct subspecies that belongs to modern-day African Elephant.
	L. exoptata	Denen Dora Member.	Undescribed Molars.[17]
Mammuthus	M. sp.	Sidi Hakoma and Denen Dora Member.	Undescribed Molars. [17]	a mammoth relative.
Palaeoloxodon recki	P. r. brumpti	Sidi Hakoma Member.[18]	Mandibles and molar fragments.	An extinct relative of Elephants that are native to Africa.

Hominidae

Hominids of the Hadar Formation
Taxa	Species	Presence	Material	Notes	Images
Australopithecus	A. afarensis	Basal Member, Denen Dora Member, Kada Hadar Member, and Sidi Hakoma Member.	Partial skeletons such as small cranial capacity, primitive occipital, basal cranium anatomy, high frequency of unicuspid third premolars, prognathic face, and primitive mandibular anatomy.	An australopithecine hominid.	AL_444-2_skull

• Ledi-Geraru

• Photo gallery from a University of Washington archaeological field season