Earliest Olduvai hominins exploited unstable environments ~ 2 million years ago

Abstract

Rapid environmental change is a catalyst for human evolution, driving dietary innovations, habitat diversification, and dispersal. However, there is a dearth of information to assess hominin adaptions to changing physiography during key evolutionary stages such as the early Pleistocene. Here we report a multiproxy dataset from Ewass Oldupa, in the Western Plio-Pleistocene rift basin of Olduvai Gorge (now Oldupai), Tanzania, to address this lacuna and offer an ecological perspective on human adaptability two million years ago. Oldupai’s earliest hominins sequentially inhabited the floodplains of sinuous channels, then river-influenced contexts, which now comprises the oldest palaeolake setting documented regionally. Early Oldowan tools reveal a homogenous technology to utilise diverse, rapidly changing environments that ranged from fern meadows to woodland mosaics, naturally burned landscapes, to lakeside woodland/palm groves as well as hyper-xeric steppes. Hominins periodically used emerging landscapes and disturbance biomes multiple times over 235,000 years, thus predating by more than 180,000 years the earliest known hominins and Oldowan industries from the Eastern side of the basin.

Fission yeast Stn1 maintains stability of repetitive DNA at subtelomere and ribosomal DNA regions

“…Fission yeast contains three chromosomes, hence six telomeres. Subtelomeres in Chromosomes I and II, ∼100 kb regions adjoining the telomeric repeats, consist of repetitive sequences shared by the four respective subtelomeres ( 24 , 44 ). Chromosome III is unique in that long arrays of rDNA repeats are closely located in the vicinity of both telomeres, whereas chromosomes I and II do not have rDNA repeats.…”

“…In this paper, subtelomeres refer to the non-rDNA sequences adjacent to telomere repeats in Chromosome I and II, and not to rDNA arrays. It is known that subtelomere structures vary in different strains; strains may contain subtelomere sequences between telomere repeats and an rDNA array at none, one, or both termini of chromosome III ( 24 , 44 ). Accordingly, different strains contain four to six subtelomere regions in total.…”

“…In a strain called JP1225, where the subtelomere structures have been extensively analyzed, the four subtelomeres derived from chromosomes I and II, and one subtelomere at the left arm of chromosome III consist of regions called SH (subtelomeric homologous) sequences, ∼15–60 kb in length, immediately adjacent to the telomere repeats ( 44 ) ( Supplementary Figure S2D ). The SH sequences characteristically consist of multiple repeat sequences shared by multiple subtelomeres with high sequence identities (>98%) ( 24 , 44 ). A strain referred to as SD5 ( SH deletion five) has been constructed by deleting all five of the SH regions in JP1225.…”

“…Fission yeast subtelomeres also contain repetitive DNA sequence elements that frequently undergo rearrangements ( 24 , 44 ). We examined the stability of repetitive DNA at telomere-proximal regions of subtelomeres in stn1-1 cells by Southern blot analysis using a TAS1 (telomere-associated sequences) probe, which recognizes sequences located ∼1 kb-centromeric from the most distal ends of chromosomes ( 38 , 41 ).…”

“…Recently, we and others revealed that Stn1 in fission yeast plays a crucial role in DNA replication at telomeres and subtelomeres adjacent to the telomeric repeats ( 21 , 22 ). Subtelomeres contain repetitive sequences, which are refractory to DNA replication and likely induce rearrangements in fission yeast ( 23 , 24 ). Temperature-sensitive stn1 mutants display replication failure at subtelomeres, resulting in immediate loss of telomeric DNA upon shifting to restrictive temperatures ( 21 , 22 ).…”